ALBERT

Description: We present high-resolution tomographic images in source areas of 26 large crustal earthquakes ( M 6.0–7.2) which occurred in Northeast Japan (Tohoku) during the past 120 yr from 1894 to 2014. Prominent low-velocity (low- V ) and high Poisson's ratio (high- ) anomalies are revealed in the crust and mantle wedge under the source areas. Beneath the volcanic front and backarc areas, the low- V and high- zones reflect arc-magma related high-temperature anomalies which are produced by joint effects of corner flow in the mantle wedge and fluids from dehydration of the subducting Pacific slab. The hot anomalies cause locally thinning and weakening of the brittle seismogenic layer above them. Low-frequency micro-earthquakes are observed in the lower crust and uppermost mantle in or around the low- V zones, which reflect ascending of arc magma and fluids from the mantle wedge to the crust. No volcano and magma exist in the forearc area due to low temperature there, hence the low- V zones in the forearc reflect fluids from the slab dehydration. The ascending fluids may have produced a ‘water wall’ in the mantle wedge and crust beneath the forearc area. When the water enters active faults in the crust, the fault-zone friction is reduced and so large earthquakes can be induced. These results indicate that the nucleation of a large earthquake is not entirely a mechanical process, but is closely associated with subduction dynamics and physical and chemical properties of rocks in the crust and upper mantle. In particular, arc magma and fluids play an important role in the seismogenesis.

Description: This study presents evidence from a survey and choice experiment on the preferences of Hispanic immigrants who entered the United States illegally for different immigration reform proposal attributes. Key components of the current competing US Senate and House immigration reform bills are considered including pathways to legal permanent residence, temporary work visas, family visitation rights, and access to medical care. The results quantify the value Hispanic immigrants place on different policy attributes and suggest that longer-term work visas are highly valued. Ability to legally work in the United States and a pathway to citizenship are substantially more valued than social services such as medical care and social security benefits.

Description: Sometimes, authorities are unable to rapidly identify the origin of a tainted product. In such cases, recalls or warnings often apply to all suppliers, even to those that had not contributed to the contamination. Traceability enables more targeted recalls by identifying the product's origin more specifically. In this article, we show how increased traceability protects the reputation of industries by limiting the size of recalls. We show the relationships between traceability and the level of food safety with many identical small farms in a competitive industry and for an industry using collective action to set rules and standards.

Description: We investigate the impact of decentralised decision-making on product quality. Comparing a cooperative and an investor-owned firm suggests that members of the cooperative have an incentive to produce too much and to free-ride on quality. Whether or not cooperatives deliver higher quality products depends on the way in which the quality of the final product is determined from the quality levels of the inputs delivered (quality aggregation) as well as the number of members of the cooperative. Empirical evidence on the Austrian wine market suggests that wines produced by cooperatives tend to be of significantly lower quality, ceteris paribus .

Description: The survival of agricultural marketing co-operatives depends on their capability of satisfying and maintaining their base of farmer members. Hypotheses regarding these two success factors are developed in neoclassical economics and transaction cost economics. They are tested with a survey of 321 members of marketing co-operatives specialising in fresh fruits and vegetables. Our results show support for both perspectives. Price paid to farmers is important for their satisfaction with the co-operative. Farmers' perceptions of transaction costs are even more important.

Description: This paper explores the demand and willingness to pay (WTP) for value-added services to chicken. Since the demand for such services are likely to be highly segmented and often applies only to a market niche, models based on assumptions of homogeneity among consumers are likely to be inappropriate. For this reason, this paper combines discrete and continuous mixing distributions to concurrently identify the size of the niche market and the heterogeneity among consumers within the market niche. Failing to account for the niche market nature of value-added services is shown to have implications for predictions of WTP, demand and total revenue.

Description: This paper analyses the impact of the recent decision by the European Union to ‘decouple’ agricultural support payments from agricultural production on Irish farmers' land market decisions. The land market participation decisions of Irish farmers are modelled using a dynamic probit model, while the extent of participation decisions is modelled using a dynamic tobit model. Decoupling does not appear to have significantly altered farmers' land market decisions. One likely explanation for this is the cross-compliance obligation for farmers to maintain land in a state fit for agricultural production in order to receive their full payments.

Description: This paper evaluates the farm-level supply and income effects from removing milk quotas and reducing producer prices with increasing direct compensatory payments. Using a panel of Belgian dairy farms, we first estimate a multi-output multi-input flexible cost function that generates a U-shaped marginal cost curve for each farm of the sample. We then embed each farm cost function in a profit-maximisation programming model that is built and calibrated for each farm in the sample. Accounting for farm heterogeneity, the simulations show how dairy farms without quotas may respond differently to changes in prices and structural changes that may take place within the dairy sector. A quota removal with a 20 per cent reduction in milk prices keeps aggregate milk supply and farm income at about the same level of the 2006 reference year.

Description: This paper analyses the impact of milk quotas on the size structure of dairy herds in two major EU milk-producing member states, Germany and the Netherlands, using Markov chain models. Four mobility indicators characterising structural change are developed and calculated. Structural change in the dairy sector as measured by the mobility measures is found to be affected by the milk quota scheme. In the quota period, mobility out of dairying is lower, but the overall and upward mobility increase. This effect is stronger in the Netherlands than in West Germany.

Description: We use a stochastic dynamic programming model to simulate the market implications of alternative foot and mouth disease scenarios in the Finnish pig sector. The model considers the dynamics of animal stock adjustment and price movements when the duration of export disruptions is unknown. Explicit treatment of these issues is crucial in the economic analysis of livestock epidemics, especially if there is a risk of a prolonged export ban. Results suggest that the risk of a prolonged ban increases disease losses considerably. It also increases economic benefits from production adjustments.

Description: Consumers' preferences for food safety characteristics are investigated with a particular focus on the existence of an embedding effect. Embedding exists if consumer valuation of food safety is insensitive to scope. We conduct between-attribute external tests for embedding in two choice experiments concerning the value of food safety attributes in minced pork and chicken breasts. We find no evidence of embedding neither when using food safety attributes that are not close substitutes and which exhibit both private and public good characteristics, nor when using food safety attributes that are closer substitutes and which have primarily private good characteristics.

Description: This paper presents an empirical investigation of the link between intangible expenses of French wine companies and their financial performance. A flexible moment-based approach is used to analyse the impact of tangible and intangible expenses on the mean, variance and skewness of profit. Econometric evidence shows that a high level of intangible expenses has a positive impact on performance by increasing the expected profit and reducing variance risk. A lower level of intangible expenses reduces risk and mean of profit of corporations. This study provides insights on the use of intangible expenses as a risk management tool.

Description: In this article, we present one of the first real-world empirical applications of state-contingent production theory. Our state-contingent behavioural model allows us to analyse production under both inefficiency and uncertainty without regard to the nature of producer risk preferences. Using farm data for Finland, we estimate a flexible production model that permits substitutability between state-contingent outputs. We test empirically and reject an assumption that has been implicit in almost all efficiency studies conducted in the last three decades, namely that the production technology is output-cubical, i.e. that outputs are not substitutable between states of nature.

Description: In this paper, a modelling approach is developed for the treatment of ‘don't know’(DK) responses, within choice experiments (CEs). A DK option is motivated by the need to allow respondents the opportunity to express uncertainty. Our model explains a DK using an entropy measure of the similarity between options given to respondents within the CE. We illustrate our model by applying it to a CE examining consumer preferences for nutrient contents in food. We find that similarity between options in a given choice set does explain the tendency for respondents to report DK.

Description: Economists frequently use choice experiments (CEs) to evaluate demand for new attributes in food products. Using a split-sample experimental design focused on demand for pork chop attributes, we find consumer inferences regarding food safety and quality to impact estimates of marginal willingness to pay, market participation, policy appropriateness and consumer welfare effects. Our results suggest that interpretation of findings should be noted as conditional on attributes included in original analyses. A split-sample experimental approach involving multiple CE designs is described and suggested to practitioners to better consider consumer inference effects in future studies.

Description: Geographical origin labels are important information and marketing tools and have recently become a central component of EU agricultural promotion. We consider demand in a non-EU export market for two distinct label types: country of origin (COO) and geographical indications (GIs). Additionally, two types of GIs, ‘protected designations of origin’ (PDOs) and ‘protected GIs’ (PGIs) are considered. Empirical findings indicate consumers’ willingness to pay varies with the oil's COO and is greater for GIs than for non-GIs from a given country. Weaker evidence that consumers value PDOs more than PGIs is also found.

Description: We determine the circumstances when the absence of public listing, often believed to be a disadvantage, makes a cooperative the unique efficient governance structure. This is established in a multi-task principal–agent model, capturing that cooperatives are not publicly listed and their CEOs have to bring the downstream enterprise to value as well as to serve upstream member interests. Not having a public listing prevents the CEO from choosing the level of the downstream activities too high. Cooperatives are uniquely efficient when the upstream marginal product multiplied with a function increasing in the strength of the chain complementarities is higher than the downstream marginal product.

Description: Branded food manufacturers vindicate the use of excess production capacities to justify their production of retailers’ brands. We study the distributor's and food manufacturer's private label (PL) strategy for production within a framework featuring endogenous store brand quality, bargaining power, possible differences in production technology and potential capacity constraints for the branded manufacturer. Depending on the structure of capacity constraint (applying to both products or to the PL only), we find that the retailer may prefer to choose an independent firm for the production of the store brand whereas the branded manufacturer is chosen in the case of excess capacity.

Description: Economists have long relied on utilitarian principles in carrying out cost–benefit analysis, but such utilitarianism is typically limited to the well-being of humans. Some prominent philosophers have argued such an approach is unjustifiably speciesist, but what are the consequences of including animal well-being in cost–benefit analysis? This paper considers this question in the context of human altruism towards animals in which people's concerns for the well-being of animals create an externality. After uncovering some conceptual challenges involved in carrying out cost–benefit analysis on animal welfare policies, we report the results of a novel experiment used to measure the public-good value of farm animal welfare, and show that although the average value in our sample is quite large, the result is due to the preferences of only a small subset of the subjects.

Description: Water theft carried out by manipulating water meters constrains volumetric pricing in semi-arid regions. Cooperative management can reduce theft and improve incentives for efficient water use by inducing peer monitoring. Using a theoretical model, we show that theft is more likely when prices are high, punishments are weak, and cooperatives are large. We also show how cooperative membership and punishment levels are determined endogenously by constraints on monitoring. We test the model on data from Tunisia for the years 2001–2003, relying on instruments that proxy for unobservable monitoring costs. The results confirm that well-designed incentives can reduce theft, and that constraints on monitoring costs affect institutional design.

Description: Crop insurance is similar to flood and hurricane insurance in that spatially correlated weather tends to cause violations of the independence assumption. Ideally, one would seek to pool uncorrelated risk drawn from the same distribution in crop insurance. This article proposes a testing procedure for the cross-sectional pooling of group units, and empirically analyzes whether the proposed test improves out-of-sample rating performance. We utilize a balanced panel of U.S. county-level corn yields for 510 counties, and the results of an out-of-sample crop insurance rating performance exercise provide economic significance to the proposed pooling methodology and results.

Description: Is low input use by poor, smallholder farmers caused by time-inconsistent behavior or by limited ability to buy inputs? Are input subsidies the best solution to stimulate input demand or are there smarter solutions? These issues are investigated by combining survey data, stated preference questions, and randomized experiments in Malawi. The demand for fertilizer at harvest time and at planting time, farm gate shadow prices for fertilizer, and the gap between the willingness-to-accept (WTA) and willingness-to-pay (WTP) prices for a standard input package were investigated. Significant effects of timing and of cash constraints were found, suggesting the possibility that smarter designs exist, such as distribution of smaller packages from harvest time to planting time.

Description: This paper studies the effect of political regime transitions on public policy using a new data set on global agricultural and food policies over a 50-year period (including data from 74 developing and developed countries over the 1955–2005 period). We find evidence that democratization leads to a reduction of agricultural taxation, an increase in agricultural subsidization, or both. The empirical findings are consistent with the predictions of the median voter model because political transitions occurred primarily in countries with a majority of farmers. The results are robust to different specifications, estimation approaches, and variable definitions.

Description: In times of highly volatile commodity markets, governments often try to protect their populations from rapidly rising food prices, which can be particularly harmful for the poor. A potential solution for food-deficit countries is to hold strategic reserves that can be called on when international prices spike. But how large should strategic stockpiles be, and what rules should govern their release? In this paper, we develop a dynamic competitive storage model for wheat in the Middle East and North Africa region, where imported wheat is the most significant component of the average diet. We analyze a strategy that sets aside wheat stockpiles, which can be used to keep domestic prices below a targeted price. Our analysis shows that if the target price is set high and reserves are adequate, the strategy can be effective and robust. Contrary to most interventions, strategic storage policies are counter-cyclical, and when the importing region is sufficiently large, a regional policy can smooth global prices. Simulations indicate that this is the case for the Middle East and North Africa region. Nevertheless, the policy is more costly than a procyclical policy similar to food stamps that uses targeted transfers to directly offset high prices with a subsidy.

Description: This is the first paper to analyze liquidity costs in agricultural futures markets based on the observed bid-ask spread (BAS) faced by market participants. The results reveal a highly liquid corn market that mostly offers order execution at minimum cost. The BAS responds negatively to volume and positively to price volatility, but also affects volume traded and price volatility. While statistically significant, these responses on a cents/bushel or a percentage basis are generally small. Liquidity costs are also virtually impervious to short-term changes in demand for spreading and trend-following trader activity, as well as differences from day-of-the-week changes in market activity. Much larger cents/bushel and percentage changes in BAS occur during commodity index trader roll periods and on USDA report release days. The roll period findings indicate a sunshine trading effect, while announcement effects identify the importance of unexpected information and adverse selection on order execution costs. Overall, our research demonstrates that the transition to electronic trading in the corn futures market has led to low and stable liquidity costs, despite the market turbulence in 2008–2009.

Description: The Minnesota Food Network is a limited liability company comprised of 52 farmers producing a variety of high-quality, sustainably produced agricultural products in southern Minnesota. The network's goal is to develop a regional food system to provide locally grown food at a price that "is fair" to both consumers and producers. This case outlines the challenges that the network faces in their efforts to expand to take advantage of a market opportunity. One of their biggest challenges is that they face high operating costs because of their disaggregated distribution system and need to purchase a distribution and storage facility and two vehicles. They will fund the purchase of a building through an angel investor. An angel investor is necessary because the network cannot sustain traditional loan payments in its current form. Students are asked to consider a number of questions pertaining to the decisions in this case outlined in the final section of the case study.

Description: To successfully market new products in a social network it is essential to identify influential individuals whose product recommendations influence the consumption choices of their peers. In this study, we use spatial econometric methods to determine how individuals revise their preferences for product attributes when exposed to product recommendations from peers, and how different individuals who vary in their degree of network connectedness exert influence on the product choices of others. We find evidence that consumers look to others for guidance from peers in their preference for subjective, taste-specific parameters, but tend not to respond to peer price choices. Our spatial methods allow us to empirically determine the influence exerted by individual members on the consumption choices of other members of the social network. We find that connected members of the social network are not always the most influential in revising the consumption choices of others. Our estimates reveal that network proximity explains only 8.8% of influence.

Description: Simulated prices from a stochastic storage model are used to examine the price impacts of speculation by rational investors who diversify their financial portfolios by holding agricultural commodity futures. The main result is that rather than destabilizing commodity prices, as is commonly believed, portfolio speculation actually reduces price volatility. Portfolio speculation can potentially destabilize a commodity's price because the additional demand for long futures by speculators is expected to drive up the cash price during both periods of low net demand, when the cash price is below average, and periods of high net demand, when the cash price is above average. Our theoretical analysis demonstrates that the higher level of inventory that is associated with portfolio speculation results in a larger release of stocks during periods of high net demand. The price simulations reveal that this stock adjustment effect is strong since overall price volatility is smaller rather than larger with portfolio speculation.

Description: This paper uses framed choice experiments to examine the preferences of smallholder farmers in Malawi regarding alternative policy-based incentives to adopt conservation practices that reduce soil erosion and increase yields. The policy incentives offered in the choice experiments included an ideal index-based crop insurance contract, an index insurance contract with basis risk, cash payments, and fertilizer subsidies. Prior to implementing the choice experiments, the farmers participated in a workshop utilizing small group-based dynamic learning games that demonstrated how index-based crop insurance contracts function. The choice experiment results indicate that most farmers preferred cash payments to index insurance contracts, even when the insurance contracts offered substantially higher expected returns. Further, more risk averse farmers were more likely to prefer cash payments than less risk averse and risk loving farmers.

Description: We develop a dynamic model to assess the effects of policy expectations on crop supply and illustrate the approach with estimates of the effects of base updating in U.S. crop programs. For corn and soybeans in the Corn Belt, the effect of base updating is relatively small because relevant crop alternatives are subject to similar policies and the alternatives are substitutes in production. Increasing acreage of one program crop to capture future payments from base updating reduces future payments from the alternative crop. We also use our model to assess the effect of base updating on acreage response to prices.

Description: A substantial share of U.S. hog producers incorporate antimicrobial drugs into their livestock's feed or water at sub-therapeutic levels to promote feed efficiency and weight gain. Recently, in response to concerns that the overuse of antibiotics in livestock could promote the development of antimicrobial drug-resistant bacteria, the U.S. Food and Drug Administration adopted a strategy to phase out the use of antibiotics for production purposes. This study uses a stochastic frontier model and data from the 2009 USDA Agricultural Resource Management Survey of feeder-to-finish hog producers to estimate the potential effects on hog output and output variability resulting from a ban on antibiotics used for growth promotion. We use propensity score nearest neighbor matching to create a balanced sample of sub-therapeutic antibiotic (STA) users and nonusers. We estimate the frontier model for the pooled sample and separately for users and non-users—which allows for a flexible interaction between STA use and the production technology. Point estimates for the matched sample indicate that STA use has a small positive effect on productivity and production risk, increasing output by 1.0–1.3% and reducing the standard deviation of unexplained output by 1.4%. The results indicate that improvements in productivity resulted exclusively from technological improvement rather than from an increase in technical efficiency.

Description: Randomized controlled trials (RCTs) in the social sciences are typically not double-blind, so participants know they are "treated" and will adjust their behavior accordingly. Such effort responses complicate the assessment of impact. To gauge the potential magnitude of effort responses we implement a conventional RCT and double-blind trial in rural Tanzania, and randomly allocate modern and traditional cowpea seed varieties to a sample of farmers. Effort responses can be quantitatively important—for our case they explain the entire "treatment effect on the treated" as measured in a conventional economic RCT. Specifically, harvests are the same for people who know they received the modern seeds and for people who did not know what type of seeds they got; however, people who knew they had received the traditional seeds did much worse. Importantly, we also find that most of the behavioral response is unobserved by the analyst, or at least not readily captured using coarse, standard controls.

Description: We investigate farm size inequality in France using agricultural censuses and farm structure surveys at the NUTS3 level (‘départements’) during the period 1970–2007. Using calculated Gini coefficients, we show that farm size inequality has not systematically increased in France. An econometric analysis of the determinants of farm size inequality reveals that policy measures significantly affected farm size inequality, with most of the measures considered decreasing it. Empirical results suggest that the main contributor was the activity of the SAFER (Société d'Aménagement Foncier et d'Etablissement Rural), a specific feature of the French farm structural policy aimed at regulating rural land management. Besides, this research highlights the great complexity of the dynamics underlying the evolution of farm size distribution.

Description: This paper analyses implementation policies of environmental quota trade, with the Flemish nutrient production rights as an example. Implementation policies concern the transaction quantity, quota reduction and prevention of speculation. They are analysed with a static and a dynamic multi-agent quota trade model. The static model with discrete non-auctioned quota trade shows that the obligation for quota sellers to entirely stop their production stimulates structural change. The dynamic model version indicates that a flat rate reduction on traded quota and measures taken to prevent speculation combined with too low penalties for overuse stimulate the total production.

Description: European cattle markets have recently undergone significant change. We explore the simultaneous impacts of agricultural policy reform and the occurrence of an animal health crisis on spatial interdependencies of calf prices of four major European Union markets. The markets are found to be integrated. Price shocks are rapidly absorbed. We find that the member state specific implementations of the 2003 Common Agricultural Policy reforms significantly affected prices of both the national market and of other member states. The blue tongue disease further induced structural change. Using counterfactual scenarios, we show that the decoupling of payments from production led to reduced calf prices.

Description: We apply a spatial price equilibrium model of the world sugar market to simulate an abolition of the European Union (EU) quota system in 2015/16. To overcome the normative nature of the approach, we calibrate the model by attaching a non-linear cost term to each trade flow. This is in some regards similar to positive mathematical programming. We suggest an economic interpretation and an econometric specification of the cost term. EU sugar production is simulated to increase from 13.3 to 15.5 million tons in case of quota abolition by 2019/20. Ten member states increase production, nine reduce it. Preferential imports are significantly reduced. Simulated effects are found to be more pronounced the higher the world market price.

Description: For a period of about 1 yr between the summers of 2010 and 2011, 25 broad-band seismographs were deployed in a roughly linear array across the eastern end of the Qaidam basin and the Qilian Shan in the northeastern Tibetan plateau. This region is probably the most suitable place to study the ongoing convergence interaction between the high Tibetan plateau and the main Asian continental plate. Low-frequency P receiver function analysis of the data provides an image of the crust and mantle down to 700 km depth. In addition to the Moho at 45–65 km depth beneath the profile, the 410 and 660 km discontinuities bounding the mantle transition zone can be identified at 400–410 and 650–660 km depths, respectively. A possible increase in temperature in the upper mantle thought to exist beneath the northern part of the high Tibetan plateau is thus confined to this part of the plateau and lower upper-mantle temperatures similar to those beneath southern Tibet occur beneath the Qaidam basin and Qilian Shan. When higher frequencies are included in the P receiver function analysis, a positive Ps converter dipping down to the south from 70–75 km depth at 37.9°N to about 110 km depth at 36°N is imaged. As this feature is only seen in high-frequency images and not in the low-frequency image, it is modelled as the positive Ps conversion from the base of an approximately 5-km-thick anisotropic layer at the top of the Asian mantle lithosphere which is currently subducting. This south-dipping converter continues to the south on the INDEPTH IV profile. S receiver function analysis completes the image of the structure below the Qilian Shan profile with the identification of the lithosphere–asthenosphere boundary (LAB). The LAB of the Asian Plate is identified for a reference slowness of 6.4 s deg –1 at 12–14 s (105–125 km depth) between 38 and 41°N below the northern part of the S receiver function profile. To the south it increases in depth such that it is at about 19 s (170 km depth) between 34 and 35°N at the southern end of the profile. The LAB of the Asian Plate occurs at similar depths on the INDEPTH IV profile at the latitudes where the INDEPTH IV and Qilian Shan profiles overlap. As on the INDEPTH IV profile to the south, between 34 and 35°N at the southern end of the Qilian Shan profile there is evidence from the S receiver functions for the LAB of a separate Tibetan Plate.

Description: Lower and upper bounds for present deformation rates across faults in central California between the San Andreas Fault and Pacific coast are estimated from a new Global Positioning System (GPS) velocity field for central, western California in light of geodetic evidence presented in a companion paper for slow, but significant deformation within the Pacific Plate between young seafloor in the eastern Pacific and older seafloor elsewhere on the plate. Transects of the GPS velocity field across the San Andreas Fault between Parkfield and San Juan Buatista, where fault slip is dominated by creep and the velocity field thus reveals the off-fault deformation, show that GPS sites in westernmost California move approximately parallel to the fault at an average rate of 3.4 ± 0.4 mm yr –1 relative to the older interior of the Pacific Plate, but only 1.8 ± 0.6 mm yr –1 if the Pacific Plate frame of reference is corrected for deformation within the plate. Modelled interseismic elastic deformation from the weakly coupled creeping segment of the San Andreas Fault is an order-of-magnitude too small to explain the southeastward motions of coastal sites in western California. Similarly, models that maximize residual viscoelastic deformation from the 1857 Fort Tejon and 1906 San Francisco earthquakes mismatch both the rates and directions of GPS site motions in central California relative to the Pacific Plate. Neither thus explains the site motions southwest of the San Andreas fault, indicating that the site motions measure deformation across faults and folds outboard of the San Andreas Fault. The non-zero site velocities thus constitute strong evidence for active folding and faulting outboard from the creeping segment of the San Andreas Fault and suggest limits of 0–2 mm yr –1 for the Rinconada Fault slip rate and 1.8 ± 0.6 to 3.4 ± 0.4 mm yr –1 for the slip rates integrated across near-coastal faults such as the Hosgri, San Gregorio and San Simeon faults.

Description: We combine new, well-determined GPS velocities from Clarion, Guadalupe and Socorro islands on young seafloor in the eastern Pacific basin with newly estimated velocities for 26 GPS sites from older seafloor in the central, western and southern parts of the Pacific Plate to test for deformation within the interior of the Pacific Plate and estimate the viscosity of the asthenosphere below the plate. Relative to a Pacific Plate reference frame defined from the velocities of the 26 GPS sites in other areas of the Pacific Plate, GPS sites on Clarion and Guadalupe islands in the eastern Pacific move 1.2 ± 0.6 mm yr –1 (1) towards S09°W ± 38° and 1.9 ± 0.3 mm yr –1 towards S19°E ± 10°, respectively. The two velocities, which are consistent within their 95 per cent uncertainties, both differ significantly from Pacific Plate motion. Transient volcanic deformation related to a 1993–1996 eruption of the Socorro Island shield volcano renders our GPS velocity from that island unreliable for the tectonic analysis although its motion is also southward like those of Clarion and Guadalupe islands. We test but reject the possibilities that drift of Earth's origin in ITRF2008 or unmodelled elastic offsets due to large-magnitude earthquakes around the Pacific rim since 1993 can be invoked to explain the apparent slow southward motions of Clarion and Guadalupe islands. Similarly, corrections to the Pacific Plate GPS velocity field for possible viscoelastic deformation triggered by large-magnitude earthquakes since 1950 also fail to explain the southward motions of the two islands. Viscoelastic models with prescribed asthenospheric viscosities lower than 1  x 10 19 Pa s instead introduce statistically significant inconsistencies into the Pacific Plate velocity field, suggesting that the viscosity of the asthenosphere below the plate is higher than 1  x 10 19 Pa s. Elastic deformation from locked Pacific–North America Plate boundary faults is also too small to explain the southward motions of the two islands. Horizontal thermal contraction of the plate interior may explain the motion observed at Clarion and Guadalupe islands, as might long-term tectonic deformation of the plate interior.

Description: In this study, a new method for computing the sensitivity of the glacial isostatic adjustment (GIA) forward solution with respect to the Earth's mantle viscosity, the so-called the forward sensitivity method (FSM), and a method for computing the gradient of data misfit with respect to viscosity parameters, the so-called adjoint-state method (ASM), are presented. These advanced formal methods complement each other in the inverse modelling of GIA-related observations. When solving this inverse problem, the first step is to calculate the forward sensitivities by the FSM and use them to fix the model parameters that do not affect the forward model solution, as well as identifying and removing redundant parts of the inferred viscosity structure. Once the viscosity model is optimized in view of the forward sensitivities, the minimization of the data misfit with respect to the viscosity parameters can be carried out by a gradient technique which makes use of the ASM. The aim is this paper is to derive the FSM and ASM in the forms that are closely associated with the forward solver of GIA developed by Martinec. Since this method is based on a continuous form of the forward model equations, which are then discretized by spectral and finite elements, we first derive the continuous forms of the FSM and ASM and then discretize them by the spectral and finite elements used in the discretization of the forward model equations. The advantage of this approach is that all three methods (forward, FSM and ASM) have the same matrix of equations and use the same methodology for the implementation of the time evolution of stresses. The only difference between the forward method and the FSM and ASM is that the different numerical differencing schemes for the time evolution of the Maxwell and generalized Maxwell viscous stresses are applied in the respective methods. However, it requires only a little extra computational time for carrying out the FSM and ASM numerically. An straightforward approach to compute the gradient of the data misfit is the brute-force method, whereby the partial derivatives of the misfit with respect to model parameters are approximated by the centred difference of two forward model runs. Although the brute-force method is useful for computing the gradient of the data misfit with respect to a small number of model parameters, it becomes expensive for a viscosity model with a large number of parameters. The ASM offers an efficient alternative for computing the gradient of the misfit since the computational time of the ASM is independent of the number of viscosity parameters. The ASM is thus highly efficient for calculating the gradient of the misfit for models with large numbers of parameters. However, the forward-model solution for each time step must be stored, hence the memory demands scale linearly with the number of time steps. This is the main drawback of the ASM.

Description: This paper deals with the determinants of out-farm migration across the European Union (EU) regions focusing on the role played by CAP payments. We add to the existing literature in three main directions. First, our analysis has broad coverage (150 EU regions over the 1990–2009 period); second, we work on the entire portfolio of CAP instruments; third, we rely on modern panel data methods. Results show that standard drivers, such as the relative income and the relative labour share, are important determinants of out-farm migration. Overall, CAP payments significantly contributed to maintain job in agriculture, though the magnitude of the economic effect has been quite moderate and heterogeneous across policy instruments. Pillar I subsidies exerted an effect more than two times greater than that of Pillar II payments.

Description: Decoupled direct payments to farmers were introduced in the European Union (EU) in the form of the Single Payment Scheme (SPS) in 2005. The 2013 Common Agriculture Policy (CAP) reform changed both the implementation of the SPS and its budget. We assess the possible effects of the 2013 CAP reform on EU land markets, particularly the capitalization of the SPS in land rental values. Our analyses suggest that the implementation details of the 2013 CAP reform will largely determine the impact of the SPS on land markets. The key considerations are the reference period for entitlement allocation, regionalization, payment differentiation, and budgetary changes. Our analysis also implies that a number of relatively minor policy changes could have substantial impacts on land markets.

Description: We examine the effect that investments in education have on household expenditure on fruits and vegetables using a two-stage model that accounts for differences in ability and heterogeneous returns to education. For this, we use the 2008 Consumer Expenditure Survey for the United States. We find that higher levels of education contribute to greater household expenditures on both fresh and processed fruits and vegetables. We find a nonlinear effect on fresh fruits and vegetables, indicating that education impacts the quality of purchases as well. Although nutritional education is often touted as important for a healthful diet, these results highlight how investments in human capital via formal education can potentially improve dietary quality as well.

Description: This article investigates the announcement effects of major USDA reports using intraday Chicago Board of Trade corn futures prices and trading volume from the electronic trading platform for July 2009 to May 2012. Focusing on intraday market reactions, we analyze the extent to which new information impacts and is rapidly reflected in prices. Results show that USDA reports contain substantial information for market participants. Strongest price reactions to the releases are found immediately after the market opens, and market reactions persist for approximately ten minutes. The electronic corn futures market quickly incorporates this new public information, and little evidence exists to support systematic under- or overreactions in prices. Other more subtle reactions occur in the last trading session before USDA announcements as traders adjust their market exposure in anticipation of the release.

Description: In this article, we explore how using imputed income data in the Survey of Income and Program Participation affects the observed relationship between household income volatility and food insufficiency. We find that measuring income volatility using imputed income data substantially understates the association between large drops in household income and food insufficiency. After excluding observations with imputed income, large drops in income are associated with a 2.1–percentage point increased probability of food insufficiency, or a 31% higher likelihood of food insufficiency.

Description: This research explores the viability of an alternative design for crop insurance based upon farmer-owned savings accounts that are regulated, monitored, and marginally assisted by the government. Such accounts could be an effective risk management tool for many farmers and could operate without major government subsidization. Relative to the current program, the proposed design should exhibit minimal moral hazard and adverse selection problems, and since farm-level risk does not have to be priced, the proposed design eliminates the premium rating difficulties that weaken actuarial soundness and trigger the need for substantial external subsidies. In addition, administrative costs should be considerably lower.

Description: The recent spikes of global food prices induced a rapid increase in mass media coverage, public policy attention, and donor funding for food security and for agriculture and rural poverty. This has occurred while the shift from low to high food prices has induced a shift in (demographic or social) location of the hunger and poverty effects, but the total number of undernourished and poor people has declined over the same period. We suggest that the observed pattern can be explained by the presence of a global urban bias on agriculture and food policy in developing countries, and we discuss whether this global urban bias may actually benefit poor farmers. We argue that the food price spikes have succeeded where others have failed in the past: to move the problems of poor and hungry farmers to the top of the policy agenda and to induce development and donor strategies to help them.

Description: Increases in crop yields and changing cropping patterns have placed stress on agribusiness handling and storage facilities. The objective of this research is to gain insight into the relationship between safety culture and safety performance, and to identify the determinants of safety culture in agribusinesses. The research suggests that investments in labor inputs such as increased training, consistent discipline, and recognition of safety achievements all increase safety culture. Furthermore, improvements in employee perceptions of safety culture have a positive impact on reducing employee injuries. Congress has recently funded nine centers to work on occupational health and safety research in agriculture, fisheries, and forestry.

Description: Relative to the gravitational potential energy of the Earth's monopole, the multipole energy has received far less attention. In this paper, we recapitulate the basic physics from first principles and derive the formulas for multipole energies in analogy to classical electrostatic theory. We focus on the zonal quadrupole energy associated with the Earth's oblateness, the dominant term in Earth's gravity field apart from the monopole. We find the gravitational energy E oblateness 10 –6 | E monopole | = +2.5 x 10 26 J. We examine the implications of E oblateness and its changes associated with long-term ‘secular’ decreases in the oblateness parameter J 2 . We find the rate of loss of E oblateness due to the Earth rounding induced by the present-day GIA is about –200 GW, an amount quite significant in the kinetic energy budget of the mantle heat engine that drives the plate tectonics that has been estimated to be ~1 TW. We also assert that the tidal braking and the global earthquake dislocations, both resulting in Earth rounding on long-term geological timescales, are accompanied with a secular decrease of E oblateness at nearly the same rate of several GW.

Description: Large-scale chemical lateral heterogeneities are inferred in the Earth's lowermost mantle by seismological studies. We explore the model space of thermochemical convection that can maintain reservoirs of dense material for a long period of time, by using similar analysis in 3-D spherical geometry. In this study, we focus on the parameters thought to be important in controlling the stability and structure of primordial dense reservoirs in the lower mantle, including the chemical density contrast between the primordial dense material and the regular mantle material (buoyancy ratio), thermal and chemical viscosity contrasts, volume fraction of primordial dense material and the Clapeyron slope of the phase transition at 660 km depth. We find that most of the findings from the 3-D Cartesian study still apply to 3-D spherical cases after slight modifications. Varying buoyancy ratio leads to different flow patterns, from rapid upwelling to stable layering; and large thermal viscosity contrasts are required to generate long wavelength chemical structures in the lower mantle. Chemical viscosity contrasts in a reasonable range have a second-order role in modifying the stability of the dense anomalies. The volume fraction of the initial primordial dense material does not effect the results with large thermal viscosity contrasts, but has significant effects on calculations with intermediate and small thermal viscosity contrasts. The volume fraction of dense material at which the flow pattern changes from unstable to stable depends on buoyancy ratio and thermal viscosity contrast. An endothermic phase transition at 660 km depth acts as a ‘filter’ allowing cold slabs to penetrate while blocking most of the dense material from penetrating to the upper mantle.

Description: Relative sea level curves contain coupled information about absolute sea level change and vertical lithospheric movement. Such curves may be constructed based on, for example tide gauge data for the most recent times and different types of geological data for ancient times. Correct account for vertical lithospheric movement is essential for estimation of reliable values of absolute sea level change from relative sea level data and vise versa. For modern times, estimates of vertical lithospheric movement may be constrained by data (e.g. GPS-based measurements), which are independent from the relative sea level data. Similar independent data do not exist for ancient times. The purpose of this study is to test two simple inversion approaches for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates for ancient times in areas where a dense coverage of relative sea level data exists and well-constrained average lithospheric movement values are known from, for example glacial isostatic adjustment (GIA) models. The inversion approaches are tested and used for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates in southwest Scandinavia from modern relative sea level data series that cover the period from 1900 to 2000. In both approaches, a priori information is required to solve the inverse problem. A priori information about the average vertical lithospheric movement in the area of interest is critical for the quality of the obtained results. The two tested inversion schemes result in estimated absolute sea level rise of ~1.2/1.3 mm yr –1 and vertical uplift rates ranging from approximately –1.4/–1.2 mm yr –1 (subsidence) to about 5.0/5.2 mm yr –1 if an a priori value of 1 mm yr –1 is used for the vertical lithospheric movement throughout the study area. In case the studied time interval is broken into two time intervals (before and after 1970), absolute sea level rise values of ~0.8/1.2 mm yr –1 (before 1970) and ~2.0 mm yr –1 (after 1970) are found. The uplift patterns resulting from the different inversions suggest that the lithospheric post-GIA response changes near the border between the Danish Basin and the Fennoscandian Shield. The obtained patterns of vertical lithospheric movement rates are comparable to results from other studies based on different and similar data types. Main differences between the inversion results and the results from other studies are caused by factors such as the simplifications included in the inversion approach, such as neglecting local sea level variation caused by the dominant wind patterns, and the a priori values chosen for the vertical uplift rates. The tests of the inversion schemes reveal that realistic values of absolute sea level rise and lithospheric uplift may be simultaneously estimated provided that reliable prior knowledge regarding the overall lithospheric uplift in the study area is available beforehand. In the presented parametrizations, only one absolute sea level change rate value is estimated for each studied time interval while several vertical movement rates are found, and the inverse estimate of absolute sea level change rate is practically insensitive with respect to the choice of a priori value of absolute sea level change, as long as the uncertainty assigned to this a priori value is kept sufficiently high.

Description: In 1356, a magnitude 6–7 earthquake occurred near Basel, in Switzerland. But recent compilations of GPS measurements reveal that measured horizontal deformation rates in northwestern continental Europe are smaller than error bars on the measurements, proving present tectonic activity, if any, is very small in this area. We propose to reconcile these apparently antinomic observations with a mechanical model of the lithosphere that takes into account the geometry of the lithosphere–asthenosphere boundary, assuming that the only loading mechanism is gravity. The lithosphere is considered to be an elastoplastic material satisfying a Von Mises plasticity criterion. The model, which is 400 km long, 360 km wide and 230 km thick, is centred near Belfort in eastern France, with its width oriented parallel to the N145°E direction. It also takes into account the real topography of both the ground surface and that of the Moho discontinuity. Not only does the model reproduce observed principal stress directions orientations, it also identifies a plastic zone that fits roughly the most seismically active domain of the region. Interestingly, a somewhat similar stress map may be produced by considering an elastic lithosphere and an ad-hoc horizontal ‘tectonic’ stress field. However, for the latter model, examination of the plasticity criterion suggests that plastic deformation should have taken place. It is concluded that the present-day stress field in this region is likely controlled by gravity and rheology, rather than by active Alpine tectonics.

Description: We have investigated variations in transition zone thickness under the Borborema Province of NE Brazil by migrating and stacking teleseismic P -wave receiver functions at 32 seismic stations in the region. The Borborema Province represents the western portion of a larger Neoproterozoic mobile belt that occupied much of northern Gondwana, where extensional processes in the Mesozoic lead to the formation of a number of intracontinental basins and ultimately continental breakup. Episodes of intraplate volcanism and uplift marked the evolution of the Province during the Cenozoic, but it is unclear whether those episodes originated from shallow or deep-seated magmatic sources. On one hand, the elliptical shape of the uplifted area, the stress pattern of the Cenozoic deformation and the time overlap between uplift and volcanism suggest doming from thermal activation due to a deep-seated mantle plume. On the other hand, geochronological dates of volcanic bodies in the Province are better understood if resulting from lithospheric erosion by a shallow, small-scale convection cell. Large temperature anomalies are expected to be associated with mantle upwellings, and constraints on the depth extent of the upwellings can be obtained from transition zone thickness. Thinning of the transition zone with respect to its nominal 250 km value is considered diagnostic for positive temperature anomalies, while thickening is considered diagnostic for negative anomalies. Our results show that transition zone thickness is normal, around 250 km, throughout the Province and suggest that thermal perturbations—if present—are confined to the upper mantle. We argue that our results are consistent with a local, shallow magmatic source for the Cenozoic intraplate volcanism of the Borborema Province, although other proposed scenarios—such as channeling of upwelling plume material along lithospheric thin spots—cannot be ruled out with our analysis.

Description: In a well-functioning futures market, the futures price at expiration equals the price of the underlying asset. This condition failed to hold in grain markets for most of 2005-2010, calling into question the ability of these markets to perform their price discovery and risk management functions. During this period, futures contracts expired up to 35% above the cash grain price. We develop a dynamic rational expectations model of commodity storage that explains how these recent convergence failures were generated by the institutional structure of the delivery system. When delivery occurs on a grain futures contract, the firm on the short side of the market provides a delivery instrument (a warehouse receipt or shipping certificate) to the firm on the long side of the market. The firm taking delivery may hold the delivery instrument indefinitely, providing it pays a daily storage rate. The futures exchange sets the maximum allowable storage rate at a fixed value. We show that non-convergence arises in equilibrium when the market price of physical grain storage exceeds the maximum storage rate on delivery instruments. We call the difference between the price of carrying physical grain and the maximum storage rate the wedge , and demonstrate theoretically and empirically that the magnitude of the non-convergence equals the expected present discounted value of a function of future wedges.

Description: Standard techniques for computed tomography imaging are not directly applicable to a carbonate rock because of the geometric complexity of its pore space. In this study, we first characterized the pore structure in Majella limestone with 30 per cent porosity. Microtomography data acquired on this rock was partitioned into three distinct domains: macropores, solid grains, and an intermediate domain made up of voxels of solid embedded with micropores below the resolution. A morphological analysis of the microtomography images shows that in Majella limestone both the solid and intermediate domains are interconnected in a manner similar to that reported previously in a less porous limestone. We however show that the macroporosity in Majella limestone is fundamentally different, in that it has a percolative backbone which may contribute significantly to its permeability. We then applied for the first time 3-D-volumetric digital image correlation (DIC) to characterize the mode of mechanical failure in this limestone. Samples were triaxially deformed over a wide range of confining pressures. Tomography imaging was performed on these samples before and after deformation. Inelastic compaction was observed at all tested pressures associated with both brittle and ductile behaviors. Our DIC analysis reveals the structure of compacting shear bands in Majella limestone deformed in the transitional regime. It also indicates an increase of geometric complexity with increasing confinement—from a planar shear band, to a curvilinear band, and ultimately to a diffuse multiplicity of bands, before shear localization is inhibited as the failure mode completes the transition to delocalized cataclastic flow.

Description: Are labels good or bad for consumers and firms? The answer may seem straightforward since labels improve information, yet economic theory reveals situations where their introduction reduces the welfare of at least some market participants. This essay reviews the theoretical literature on labels in order to identify and explain the main reasons that may cause labeling to produce undesirable side-effects. In contrast to earlier reviews that either concentrate on narrow topics or treat the subject in a more or less informal way, we bring together the main results from all the relevant topics by presenting and discussing the assumptions and model-building techniques that underpin them. The advantage of this approach is that it identifies the origin of the differences between results, thus allowing the synthesis of results that sometimes appear even to be contradictory. We focus on "quality labels" and examine the impact of labeling on market structure, the side-effects of costly certification, issues related to the label's trustworthiness, the rationale for mandatory vs. voluntary labeling, the level at which the label's standard is set according to the agency that selects it, the political economy of labels, that is, pro- or anti-label lobbying, lobbying to affect the label's standard, and lobbying in favor or against the label's mandatory imposition. These topics cover a wide range of applications, including Genetically Modified Organism (GMOs), organic produce, geographic indicators, controlled origin, eco-labels, etc. We conclude by identifying topics that require further research.

Description: Can food prices cause social unrest? Throughout history, riots have frequently broken out, ostensibly as a consequence of high food prices. Using monthly data at the international level, this article studies the impact of food prices – food price levels as well as food price volatility – on social unrest. Because food prices and social unrest are jointly determined, data on natural disasters are used to identify the causal relationship flowing from food price levels to social unrest. Results indicate that for the period 1990–2011, food price increases have led to increases in social unrest, whereas food price volatility has not been associated with increases in social unrest. These results are robust to alternative definitions of social unrest, to using real or nominal prices, to using commodity-specific price indices instead of aggregated price indices, to alternative definitions of the instrumental variable, to alternative definitions of volatility, and to controlling for non-food-related social unrest.

Description: A recently developed testing procedure is used to detect and date-stamp explosive episodes ("bubbles") in corn, soybean, and wheat futures markets during 2004–2013. We find that the markets experienced price explosiveness only approximately two percent of the time and, when bubbles do occur, they are generally short-lived and small in magnitude. The correspondence between observed price spikes and bubbles is rather low, with a large portion of the price explosiveness occurring during downward price movements. Commodity index trader positions do not significantly affect the probability of a positive bubble occurring in grain futures markets, which directly contradicts the argument (the "Masters Hypothesis") that waves of index investment distorted underlying supply-and-demand relationships and led to a series of massive bubbles in agricultural futures markets. In addition, commodity index trader positions tend to reduce negative bubble occurrence, while general speculative activity as measured by Working's T reduces the probability of a positive bubble. There is some evidence that the positions of noncommercial traders have a direct effect on positive bubble occurrence, but the effect declines when accounting for the composition of other traders in the market. Overall, speculation has little effect or negative effects on price explosiveness. Finally, positive bubbles are more likely to occur in the presence of low inventories, strong exports, a weak U.S. dollar, and booming economic growth, whereas negative bubbles are more likely to occur with large inventories, weak exports, and stagnant economic growth.

Description: Wide-angle reflection/refraction seismic profiles were recorded across the Cyprus Arc, the plate boundary between the African Plate and the Aegean–Anatolian microplate, from the Eratosthenes Seamount to the Hecataeus Rise immediately south of Cyprus. The resultant models were able to resolve detail of significant lateral velocity variations, though the deepest crust and Moho are not well resolved from the seismic data alone. Conclusions from the modelling suggest that (i) Eratosthenes Seamount consists of continental crust but exhibits a laterally variable velocity structure with a thicker middle crust and thinner lower crust to the northeast; (ii) the Hecataeus Rise has a thick sedimentary rock cover on an indeterminate crust (likely continental) and the crust is significantly thinner than Eratosthenes Seamount based on gravity modelling; (iii) high velocity basement blocks, coincident with highs in the magnetic field, occur in the deep water between Eratosthenes and Hecataeus, and are separated and bounded by deep low-velocity troughs and (iv) one of the high velocity blocks runs parallel to the Cyprus Arc, while the other two appear linked based on the magnetic data and run NW–SE, parallel to the margin of the Hecataeus Rise. The high velocity block beneath the edge of Eratosthenes Seamount is interpreted as an older magmatic intrusion while the linked high velocity blocks along Hecataeus Rise are interpreted as deformed remnant Tethyan oceanic crust or mafic intrusives from the NNW–SSE oriented transform margin marking the northern boundary of Eratosthenes Seamount. Eratosthenes Seamount, the northwestern limit of rifted continental crust from the Levant Margin, is part of a jagged rifted margin transected by transform faults on the northern edge of the lower African Plate that is being obliquely subducted under the Aegean–Anatolian upper plate. The thicker crust of Eratosthenes Seamount may be acting as an asperity on the subducting slab, locally locking up subduction of the Cyprus Arc on its northern margin, while deformed Tethyan oceanic crust remains trapped between its northeastern margin and the Hecataeus Rise.

Description: We present an up-to-date high resolution picture of the ongoing crustal deformation field of Italy, based on an extensive combination of permanent and non-permanent GPS observations carried out since 1994. In addition, we present an updated map of contemporary S Hmax orientations computed by a multidisciplinary data set of well-constrained stress indicators, including both published results and novel analyses. The comparison of stress and geodetic strain-rates directions reveals that both patterns are near-parallel over a large part of the investigated area, highlighting that crustal stress and surface deformation are driven by the same mechanism. The comparison of the azimuthal patterns of surface strain and mantle deformation shows a modest correlation on the Alps and a low correlation along the Apennines chain and the Calabro-Peloritan Arc. Along the Apennines chain, this feature suggests the occurrence of significant strain partitioning and crust–mantle mechanical decoupling. Along the Calabro-Peloritan Arc, the apparent low correlation reflects a different mantle–crust mechanism of deformation to the ongoing subduction and rollback of the Ionian slab. In addition, the superposition of regional/local effects related to second-order sources (crustal lateral density changes, strength contrasts), which at regional/local scale modulate the crustal stress/strain-rate pattern, cannot be ruled out.

Description: A series of linear analysis was performed on the onset of thermal convection of highly compressible fluids, in order to deepen the fundamental insights into the mantle convection of massive super-Earths in the presence of strong adiabatic compression. We consider the temporal evolution (growth or decay) of an infinitesimal perturbation superimposed to a highly compressible fluid which is in a hydrostatic (motionless) and conductive state in a basally heated horizontal layer. As a model of pressure-dependence in material properties, we employed an exponential decrease in thermal expansivity α and exponential increase in (reference) density with depth. The linearized equations for conservation of mass, momentum and internal (thermal) energy are numerically solved for the critical Rayleigh number as well as the vertical profiles of eigenfunctions for infinitesimal perturbations. The above calculations are repeatedly carried out by systematically varying (i) the dissipation number (Di), (ii) the temperature at the top surface and (iii) the magnitude of pressure-dependence in α and . Our analysis demonstrated that the onset of thermal convection is strongly affected by the adiabatic compression, in response to the changes in the static stability of thermal stratification in the fluid layer. For sufficiently large Di where a thick sublayer of stable stratification develops in the layer, for example, the critical Rayleigh number explosively increases with Di, together with drastic decreases in the length scales of perturbations both in vertical and horizontal directions. In particular, for very large Di, a thick ‘stratosphere’ occurs in the fluid layer where the vertical motion is significantly suppressed, resulting in a shrink of the incipient convection in a thin sublayer of unstable thermal stratification. In addition, when Di exceeds a threshold value above which a thermal stratification becomes stable in the entire layer, no perturbation is allowed to grow with time regardless of the Rayleigh number and/or the horizontal wavelength. We also found that the effect of adiabatic compression becomes prominent for higher temperature at the top surface of the fluid layer. These findings may imply the crucial importance of adiabatic compression in understanding the dynamics and evolution of the mantles of massive super-Earths, particularly for those orbiting their parent stars very closely.

Description: In this paper, we propose an approach to compute the coseismic Earth's volume change based on a spherical-Earth elastic dislocation theory. We present a general expression of the Earth's volume change for three typical dislocations: the shear, tensile and explosion sources. We conduct a case study for the 2004 Sumatra earthquake ( M w 9.3), the 2010 Chile earthquake ( M w 8.8), the 2011 Tohoku-Oki earthquake ( M w 9.0) and the 2013 Okhotsk Sea earthquake ( M w 8.3). The results show that mega-thrust earthquakes make the Earth expand and earthquakes along a normal fault make the Earth contract. We compare the volume changes computed for finite fault models and a point source of the 2011 Tohoku-Oki earthquake ( M w 9.0). The big difference of the results indicates that the coseismic changes in the Earth's volume (or the mean radius) are strongly dependent on the earthquakes’ focal mechanism, especially the depth and the dip angle. Then we estimate the cumulative volume changes by historical earthquakes ( M w ≥ 7.0) since 1960, and obtain an Earth mean radius expanding rate about 0.011 mm yr –1 .

Description: We present the crustal resistivity structure of the Pamir and Southern Tian Shan orogenic belts at the northwestern promontory of the India–Asia collision zone. The magnetotelluric (MT) data were recorded along a roughly north–south trending, 350 km long corridor from the Pamir Plateau in southern Tajikistan across the Pamir frontal ranges, the Alai Valley and the southwestern Tian Shan to Osh in the Kyrgyz part of the Fergana Basin. In total, we measured at 178 sites, whereof 26 combine broad band and long period recordings. One of the most intriguing features of the 2-D and 3-D inversion results is a laterally extended zone of high electrical conductivity below the Pamir Plateau, with resistivities below 1 m, starting at a depth of ~10–15 km. The high conductivity can be explained with the presence of partially molten rocks at middle to lower crustal levels, possibly related to ongoing migmatization and/or middle/lower crustal flow underneath the Southern Pamir. This interpretation is consistent with a low velocity zone found from local earthquake tomography, relatively high v p / v s ratios, elevated surface heat flow, and thermomechanical modelling suggesting that melting temperatures are reached in the felsic middle crust. In the upper crust of the Pamir and Tian Shan, the Palaeozoic–Mesozoic suture zones appear as electrically conductive, whereas the compact metamorphic rocks of the Muskol-Shatput Dome of the Central Pamir are highly resistive. The intra-montane basin of the Alai Valley—sandwiched between the Pamir and Tian Shan—exhibits a generally conductive upper crust that bifurcates into two conductors at depth. One of them connects to the active Main Pamir Thrust, which is absorbing most of today's convergence between the Pamir and the Tian Shan. Several deeper zones of high conductivity in the middle and lower crust of Central and Northern Pamir likely record fluid release due to metamorphism associated with active continental subduction/delamination.

Description: A new model of the deglaciation history of Antarctica over the past 25 kyr has been developed, which we refer to herein as ICE-6G_C (VM5a). This revision of its predecessor ICE-5G (VM2) has been constrained to fit all available geological and geodetic observations, consisting of: (1) the present day uplift rates at 42 sites estimated from GPS measurements, (2) ice thickness change at 62 locations estimated from exposure-age dating, (3) Holocene relative sea level histories from 12 locations estimated on the basis of radiocarbon dating and (4) age of the onset of marine sedimentation at nine locations along the Antarctic shelf also estimated on the basis of 14 C dating. Our new model fits the totality of these data well. An additional nine GPS-determined site velocities are also estimated for locations known to be influenced by modern ice loss from the Pine Island Bay and Northern Antarctic Peninsula regions. At the 42 locations not influenced by modern ice loss, the quality of the fit of postglacial rebound model ICE-6G_C (VM5A) is characterized by a weighted root mean square residual of 0.9 mm yr –1 . The Southern Antarctic Peninsula is inferred to be rising at 2 mm yr –1 , requiring there to be less Holocene ice loss there than in the prior model ICE-5G (VM2). The East Antarctica coast is rising at approximately 1 mm yr –1 , requiring ice loss from this region to have been small since Last Glacial Maximum. The Ellsworth Mountains, at the base of the Antarctic Peninsula, are inferred to be rising at 5–8 mm yr –1 , indicating large ice loss from this area during deglaciation that is poorly sampled by geological data. Horizontal deformation of the Antarctic Plate is minor with two exceptions. First, O'Higgins, at the tip of the Antarctic Peninsula, is moving southeast at a significant 2 mm yr –1 relative to the Antarctic Plate. Secondly, the margins of the Ronne and Ross Ice Shelves are moving horizontally away from the shelf centres at an approximate rate of 0.8 mm yr –1 , in viscous response to the early Holocene unloading of ice from the current locations of the ice shelf centers. ICE-6G_C (VM5A) fits the horizontal observations well (wrms residual speed of 0.7 mm yr –1 ), there being no need to invoke any influence of lateral variation in mantle viscosity. ICE-6G_C (VM5A) differs in several respects from the recently published W12A model of Whitehouse et al. First, the upper-mantle viscosity in VM5a is 5 10 20 Pa s, half that in W12A. The VM5a profile, which is identical to that inferred on the basis of the Fennoscandian relaxation spectrum, North American relative sea level histories and Earth rotation constraints, when coupled with the revised ICE-6G_C deglaciation history, fits all of the available constraints. Secondly, the net contribution of Antarctica ice loss to global sea level rise is 13.6 m, 2/3 greater than the 8 m in W12A. Thirdly, ice loss occurs quickly from 12 to 5 ka, and the contribution to global sea level rise during Meltwater Pulse 1B (11.5 ka) is large (5 m), consistent with sedimentation constraints from cores from the Antarctica ice shelf. Fourthly, in ICE-6G_C there is no ice gain in the East Antarctica interior, as there is in W12A. Finally, the new model of Antarctic deglaciation reconciles the global constraint upon the global mass loss during deglaciation provided by the Barbados record of relative sea level history when coupled with the Northern Hemisphere counterpart of this new model.

Description: Up to now, most nutritional policies have been set up to inform consumers about the health benefits induced by more balanced diets. Reviews of the impacts of these policies show that the effects are often modest. This has led governments to implement, in more recent times, policies focused on the market environment, especially on the characteristics of the food supply. The goal of this paper is to review theoretical and empirical studies focusing on changes in the food supply induced by alternative policies, and to attempt to draw from them policy guidelines and conjectures to test in future research.

Description: The Himalaya is the result of the on-going convergence and collision of India and Asia. The internal configuration and processes that govern the rise of the Himalayan Mountains and Tibetan Plateau are crucial to understand continental collision zones. However, knowledge of the prior configuration of the colliding plates is equally important, since inherited (pre-orogenic/basement) structures can undeniably influence the development of the orogenic architecture throughout the orogen's cycle of collision and eventual collapse. Three northeast-trending palaeotopographic ridges of faulted Precambrian Indian basement underlie the Ganga basin south of the Himalaya. Our paper illustrates a crustal-scale fault origin for these ridges and succeeds in determining how far north beneath the Himalayan system they extend and how they ultimately govern the location of upper crustal faults in southern Tibet. Spectrally filtered EGM2008 Bouguer gravity data and edges in its horizontal gradient at different source depths (‘gravity worms’) over northern Peninsular India, the Himalaya and southern Tibet reveal several continuous Himalayan cross-strike discontinuities interpreted to represent crustal faults. Gravity lineaments in Peninsular India coincide with edges of the Precambrian basement ridges and megakinks up to 100 km wide develop in foreland cover sequences between the interpreted basement faults. The interpreted basement faults project northward beneath the Himalayan system and southern Tibet. Our results suggest that several active Himalayan cross-strike faults, such as the ones related to many graben in southern Tibet, are rooted in the underplated Indian lower crust or step en échelon along interpreted basement faults. Our interpretation thus suggests that south Tibet graben are spatially related to deep-seated crustal-scale faults rooted in the underplated Indian crust. These major discontinuities partition the Himalayan range into distinct zones, and could ultimately contribute to lateral variability in tectonic evolution along the orogen's strike.

Description: We explore the impact of deep ductile shear zones on post-seismic deformation following a finite length strike-slip earthquake. We show that the pattern of post-seismic vertical surface deformation surrounding the fault is a discriminant for the existence of high viscosities immediately below the seismogenic layer, regardless of whether the model contains purely distributed creep or also includes a component of localized creep at subseismogenic depths. Post-seismic deformation characterized by initially fast relaxation followed by a slower relaxation is predicted by models that include both localized creep in a subseismogenic shear zone and distributed creep in the surrounding region, even if they only contain steady Maxwell viscoelasticity. This post-seismic deformation is similar to that in models that approximate the ductile lithosphere and/or asthenosphere with Burgers viscoelasticity. We find that the post-seismic deformation following the 1997 M w 7.6 Manyi, China, earthquake, is consistent with a post-seismic model composed of a lower Maxwell viscoelastic region with viscosity 10 19 Pa s and a 5 km wide, Maxwell viscoelastic shear zone with viscosity 10 18 Pa s beneath the fault.

Description: The Amundsen Sea Embayment of West Antarctica represents a key component in the tectonic history of Antarctic–New Zealand continental breakup. The region played a major role in the plate-kinematic development of the southern Pacific from the inferred collision of the Hikurangi Plateau with the Gondwana subduction margin at approximately 110–100 Ma to the evolution of the West Antarctic Rift System. However, little is known about the crustal architecture and the tectonic processes creating the embayment. During two ‘RV Polarstern’ expeditions in 2006 and 2010 a large geophysical data set was collected consisting of seismic-refraction and reflection data, ship-borne gravity and helicopter-borne magnetic measurements. Two P -wave velocity–depth models based on forward traveltime modelling of nine ocean bottom hydrophone recordings provide an insight into the lithospheric structure beneath the Amundsen Sea Embayment. Seismic-reflection data image the sedimentary architecture and the top-of-basement. The seismic data provide constraints for 2-D gravity modelling, which supports and complements P -wave modelling. Our final model shows 10–14-km-thick stretched continental crust at the continental rise that thickens to as much as 28 km beneath the inner shelf. The homogenous crustal architecture of the continental rise, including horst and graben structures are interpreted as indicating that wide-mode rifting affected the entire region. We observe a high-velocity layer of variable thickness beneath the margin and related it, contrary to other ‘normal volcanic type margins’, to a proposed magma flow along the base of the crust from beneath eastern Marie Byrd Land—West Antarctica to the Marie Byrd Seamount province. Furthermore, we discuss the possibility of upper mantle serpentinization by seawater penetration at the Marie Byrd Seamount province. Hints of seaward-dipping reflectors indicate some degree of volcanism in the area after break-up. A set of gravity anomaly data indicate several phases of fully developed and failed rift systems, including a possible branch of the West Antarctic Rift System in the Amundsen Sea Embayment.

Description: Geophysical data are the main source of information about the subsurface. Geophysical techniques are, however, highly non-unique in determining specific physical parameters and boundaries of subsurface objects. To obtain actual physical information, an inversion process is often applied, in which measurements at or above the Earth surface are inverted into a 2- or 3-D subsurface spatial distribution of the physical property. Interpreting these models into structural objects, related to physical processes, requires a priori knowledge and expert analysis which is susceptible to subjective choices and is therefore often non-repeatable. In this research, we implemented a recently introduced object-based approach to interpret the 3-D inversion results of a single geophysical technique using the available a priori information and the physical and geometrical characteristics of the interpreted objects. The introduced methodology is semi-automatic and repeatable, and allows the extraction of subsurface structures using 3-D object-oriented image analysis (3-D OOA) in an objective knowledge–based classification scheme. The approach allows for a semi-objective setting of thresholds that can be tested and, if necessary, changed in a very fast and efficient way. These changes require only changing the thresholds used in a so-called ruleset, which is composed of algorithms that extract objects from a 3-D data cube. The approach is tested on a synthetic model, which is based on a priori knowledge on objects present in the study area (Tanzania). Object characteristics and thresholds were well defined in a 3-D histogram of velocity versus depth, and objects were fully retrieved. The real model results showed how 3-D OOA can deal with realistic 3-D subsurface conditions in which the boundaries become fuzzy, the object extensions become unclear and the model characteristics vary with depth due to the different physical conditions. As expected, the 3-D histogram of the real data was substantially more complex. Still, the 3-D OOA-derived objects were extracted based on their velocity and their depth location. Spatially defined boundaries, based on physical variations, can improve the modelling with spatially dependent parameter information. With 3-D OOA, the non-uniqueness on the location of objects and their physical properties can be potentially significantly reduced.

Description: We estimate Eurasia-North America Plate motion rotations at ~1-Myr intervals for the past 20 Myr from more than 11 000 crossings of 21 magnetic reversals from Chron 1n (0.78 Ma) to C6no (19.72 Ma) and flow lines digitized from the Charlie Gibbs, Bight and Molloy fracture zones and transform faults. Adjusted for outward displacement, the 21 best-fitting rotations determined from a simultaneous inversion of the numerous kinematic data reconstruct the reversal crossings with weighted root mean square misfits of only 1–2 km and 0.2–7 km for the transform fault and fracture zone crossings. The new rotations clearly define a ~1000 km southward shift of the rotation pole and 20 per cent slowdown in seafloor spreading rates between 7 and 6 Ma, preceded by apparently steady plate motion from 19.7 to ~7 Ma. Data for times since C3An.2 (6.7 Ma) are well fit by a stationary pole of rotation and constant rate of angular opening, consistent with steady motion since 6.7 Ma. The southward shift of the rotation pole at 7–6 Ma implies that Eurasia-North America motion in northeastern Asia changed from slowly convergent before 7 Ma to slowly divergent afterward. Crossings of magnetic reversals C1n through C3An.1 (6.0 Ma) are well fit everywhere in the Arctic basin and south to the Azores triple junction, indicating that the Eurasia and North America plates have not deformed along their mutual boundary since at least 6.0 Ma. However, the new rotations systematically overrotate magnetic lineations older than C3An.1 (6.0 Ma) within 200 km of the Azores triple junction and also overrotate lineations older than C5n along the Gakkel Ridge in the Arctic Basin. Barring misidentifications of the magnetic anomalies in those areas, the pattern and magnitude of the systematic misfits imply that slow (~1 mm yr –1 ) distributed or microplate deformation occurred in one or both regions.

Description: Here we inverted the GPS data to infer the coseismic slip of the Tohoku-Oki earthquake and the time-dependent afterslip distribution in the 4 months following the main shock. The Tohoku-Oki earthquake showed an unexpected magnitude and a characteristic depth-dependent differentiation of seismic energy radiation. In this context the estimation and comparison of the distribution of the fault portions that slip coseismically and post-seismically contribute to a better understanding of the variation of frictional characteristics of the plate interface. The inferred coseismic slip extends in a relatively compact region located updip from the hypocentre and reaches its highest value (about 60 m) near the trench. Afterslip occurs mostly outside the coseismic rupture and is distributed in two main modal centres. It reaches its largest values in an area located downdip of the coseismic slip and extends to a depth of 80 km. In the depth range between 30 and 50 km afterslip overlaps the portion of the fault that experienced historical moderate earthquakes, high-frequency seismic radiation and thrust-type aftershocks. The behaviour of this area can be explained by a rheologically heterogeneous region made of a ductile fault matrix interspersed with compact brittle asperities. On the contrary, the region beneath 50–60 km depth is probably characterized by a fully velocity strengthening behaviour. Southern afterslip, located off-Chiba Prefecture, is probably related to the M w 7.9 Ibaraki-Oki aftershock. The northward extension of the afterslip stops at a latitude of about 40°N, just south of the off-Aomori region. This may be related to three large events occurred in this area during the last century and the consequent strong coupling or complete depletion of the accumulated strain that characterize this region.

Description: With the rise of behavioural economics has come the belief that decision-making biases justify paternalistic policies. Such views challenge the notion of consumer sovereignty and the validity of traditional approaches of economic welfare analysis. While behavioural economics might improve the effectiveness of policies that are already justified on some other market-failure grounds, this article argues that the existence of cognitive failures, alone, do not justify government regulation. If one abandons the idea that consumers know what is in their best interest, judging the merits of policies becomes arbitrary and reflects only what a paternalist wants for others. The typical behavioural economic experiment occurs with college students devoid of real-world context. The biases found in such setting may not extrapolate well to conditions where people have more experience and knowledge, and where they can learn from past mistakes. Even when behavioural biases persist in the ‘real world’, consumers face incentives to engage in activities that protect them from the adverse consequences of the biases, and public policies that shield people from such consequences reduce incentives to self-regulate. The article concludes with some ideas for future research and a discussion of the merits of freedom of choice.

Description: In consequence of strong changes in general economic conditions, adjustments in the agricultural sector can be expected. To date, however, there are only few policy impact analyses on agricultural investments in a dynamic-stochastic context. The objective of this paper is to develop a real options market model which allows the impact assessment of different political schemes. The model combines genetic algorithms and stochastic simulation. Simulations of the model show that investment subsidies and production ceilings are preferable to price floors because the welfare is less reduced for a given stimulation of the willingness to invest.

Description: The aim of this paper is to study farmers' participation in rural development policy (RDP) measures. We investigate to what extent regional RDP priorities are driven by regional characteristics and moreover, whether regional-level policy priorities help to explain farmers' participation in RDP measures. We estimate a multilevel binary choice model that includes both farm-level and regional-level explanatory variables. We conclude that regional governments select RDP priorities based on the specific features of their region. Regional policy priorities play an important role in explaining farmers' participation in agri-environmental schemes but not in measures aimed at improving farmer competitiveness.

Description: The distinction between single farm payments (SFP) and counter-cyclical payments (CCPs) is mainly based on theory. Due to a lack of empirical comparative studies between these payments, it is difficult to confirm the claim that CCPs are more distorting. This paper provides a comparative analysis of these payments and quantifies the impact of such payments in the presence of debt constraints. The main findings are that CCPs are more distorting than SFP. However, the magnitude of the impact estimates is not as large as suggested by the different treatment received by both support programmes in the WTO negotiations.

Description: We present a revised interpretation of magnetic anomalies and fracture zones on the Southwest Indian Ridge (SWIR; Africa–Antarctica) and the Southeast Indian Ridge (SEIR; Capricorn–Antarctica) and use them to calculate 2-plate finite rotations for anomalies 34 to 20 (84 to 43 Ma). Central Indian Ridge (CIR; Capricorn–Africa) rotations are calculated by summing the SWIR and SEIR rotations. These rotations provide a high-resolution record of changes in the motion of India and Africa at the time of the onset of the Reunion plume head. An analysis of the relative velocities of India, Africa and Antarctica leads to a refinement of previous observations that the speedup of India relative to the mantle was accompanied by a slowdown of Africa. The most rapid slowdown of Africa occurs around Chron 32Ay (71 Ma), the time when India's motion relative to Africa notably starts to accelerate. Using the most recent Geomagnetic Polarity Timescale (GTS12) we show that India's velocity relative to Africa was characterized by an acceleration from roughly 60 to 180 mm yr –1 between 71 and 66 Ma, a short pulse of superfast motion (~180 mm yr –1 ) between 66 and 63 Ma, an abrupt slowdown to 120 mm yr –1 between 63 and 62 Ma, and then a long period (63 to 47 Ma) of gradual slowing, but still fast motion (~100 mm yr –1 ), which ends with a rapid slowdown after Chron 21o (47 Ma). Changes in the velocities of Africa and India with respect to the mantle follow a similar pattern. The fastest motion of India relative to the mantle, ~220 mm yr –1 , occurs during Chron 29R. The SWIR rotations constrain three significant changes in the migration path of the Africa–Antarctic stage poles: following Chron 33y (73 Ma), following Chron 31y (68 Ma), and following Chron 24o (54 Ma). The change in the migration path of the SWIR stage poles following Chron 33y is coincident with the most rapid slowdown in Africa's motion. The change in the migration path after Chron 31y, although coincident with the most rapid acceleration of India's northward motion, may be related to changes in ridge push forces on the SWIR associated with the onset of extension along the Bain transform fault zone. The initial slowdown in India's motion relative to Africa between 63 and 62 Ma is more abrupt than predictions based on published plume head force models, suggesting it might have been caused by a change in plate boundary forces. The abrupt change in the migration path of the SWIR stage poles after Chron 24o is not associated with major changes in the velocities of either Africa or India and may reflect Atlantic basin plate motion changes associated with the arrival at the Earth's surface of the Iceland plume head. The abruptness of India's slowdown after Chron 21o is consistent with a collision event.

Description: Thin plate flexure theory provides an accurate model for the response of the lithosphere to vertical loads on horizontal length scales ranging from tens to hundreds of kilometres. Examples include flexure at seamounts, fracture zones, sedimentary basins and subduction zones. When applying this theory to real world situations, most studies assume a locally uniform plate thickness to enable simple Fourier transform solutions. However, in cases where the amplitude of the flexure is prominent, such as subduction zones, or there are rapid variations in seafloor age, such as fracture zones, these models are inadequate. Here we present a computationally efficient algorithm for solving the thin plate flexure equation for non-uniform plate thickness and arbitrary vertical load. The iterative scheme takes advantage of the 2-D fast Fourier transform to perform calculations in both the spatial and spectral domains, resulting in an accurate and computationally efficient solution. We illustrate the accuracy of the method through comparisons with known analytic solutions. Finally, we present results from three simple models demonstrating the differences in trench outer rise flexure when 2-D variations in plate rigidity and applied bending moment are taken into account. Although we focus our analysis on ocean trench flexure, the method is applicable to other 2-D flexure problems having spatial rigidity variations such as seamount loading of a thermally eroded lithosphere or flexure across the continental–oceanic crust boundary.

Description: Theory has been long established for computing the elastic response of a spherically symmetric terrestrial planetary body to both body tide and surface loading forces. However, for a planet with laterally heterogeneous mantle structure, the response is usually computed using a fully numerical approach. In this paper, we develop a semi-analytic method based on perturbation theory to solve for the elastic response of a planetary body with lateral heterogeneities in its mantle. We present a derivation of the governing equations for our second-order perturbation method and use them to study the high-order tidal effects caused by mode coupling between degree-2 body tide forcing and the laterally heterogeneous elastic structure of the mantle. We test our method by applying it to the Moon in which small long-wavelength lateral heterogeneities are assumed to exist in the elastic moduli of the lunar mantle. The tidal response of the Moon is determined mode by mode, for lateral heterogeneities with different depth ranges within the mantle and different horizontal scales. Our perturbation method solutions are compared with numerical results, showing remarkable agreement between the two methods. We conclude that our perturbation method provides accurate results and can be adapted to address a variety of forward and inverse response problems.

Description: This article discusses the current state of contract theory and its usefulness for conceptualizing issues related to agricultural contracting. The paper will explore the limitations of existing theory for applied work, and what methodological improvements are needed to enhance the usefulness of the theory to agricultural economists. One pervasive problem is that the economic literature on contracts is rather fragmented and the various methodological strands are narrow in their focus. As such, agricultural economists should engage in methodological research to develop applied contracting models that can capture higher-order features of real-world agricultural contracts while delivering generalizable comparative statics predictions because contracting continues to expand along the entire modern food marketing channel. In the latter part of this article, a simple model is developed to illustrate how classic methodological approaches can be combined with recent developments in contract and game theory to construct applied theory models that are useful for capturing some important features of agricultural contracts.

Description: We examine enrollment in the U.S. Medicaid and Supplemental Nutrition Assistance Programs (SNAP) and find that while SNAP-eligible adults in poor physical health and with multiple chronic conditions are more likely to jointly enroll in SNAP and Medicaid, they are less likely to enroll in SNAP alone. We also find that the conditional probability of SNAP enrollment given Medicaid participation is higher for individuals with multiple chronic conditions. As a result, the expansion of Medicaid and state policies that promote enrollment coordination between SNAP and Medicaid are expected to increase the number of individuals in SNAP with chronic medical conditions.

Description: At odds with a vast body of economic evidence reporting exceptionally high rates of return to investments in agricultural research and development (R&D), growth in public R&D spending for food and agriculture has slowed in numerous, especially rich, countries worldwide. The observed R&D spending behavior is consistent with a determination that the reported rates of return are perceived as implausible by policy makers. We examine this notion by scrutinizing 2,242 investment evaluations reported in 372 separate studies from 1958 to 2011. We find that the internal rate of return (IRR) is the predominant summary measure of investment performance used in the literature despite methodological criticisms dating back more than a half century. The reported IRRs imply rates of return that are implausibly high. We investigate the reasons for these implausibly high estimates by analytically comparing the IRR to the modified internal rate of return (MIRR). The MIRR addresses several methodological concerns with using the IRR, has the intuitive interpretation as the annual compounding interest rate paid by an investment, and is directly related to the benefit–cost ratio. To obtain more credible rate of return estimates, we then develop a novel method for recalibrating previously reported IRR estimates using the MIRR when there is limited information on an investment's stream of benefits and costs. Our recalibrated estimates of the rate of return are more modest (median of 9.8% versus 39% per year); however, they are still substantial enough to question the current scaling back of public agricultural R&D spending in many countries.

Description: Information and communications technologies have spread rapidly in developing countries. We investigate the impact of mobile phones on traders' search behavior in Niger by constructing a theoretical model of search in which traders engage in sequential search for the optimal sales price. Using a trader panel dataset spanning 2005–2007, we find empirical support for the model in that the duration of mobile phone coverage is associated with increased search activity. This effect evolves dynamically over time and is stronger for larger traders, who engage in arbitrage over longer distances. Results provide empirical evidence for the observed linkages between mobile telephony and price dispersion.

Description: Teleseismic data recorded at 13 broad-band seismological stations across northwest part of the Tethyan Himalaya and eastern Ladakh are analysed to determine the seismic characteristics of the crust and upper mantle beneath the northwest India–Asia collision zone. The receiver functions computed from teleseismic P- waveform for a wide range of backazimuth show strong azimuthal variation in the Indus suture zone (ISZ), the zone which marks the collision and subsequent subduction of both the Tethyan oceanic plate and Indian continental plate beneath Eurasia. The teleseismic waves piercing the ISZ do not show clear P -to- S ( Ps ) converted phase at the depth of Moho. In contrast, the waves piercing the Karakoram zone, Ladakh batholith and the Tethyan Himalayan region south of the ISZ clearly show the Moho converted Ps phase and corresponding inverted models reveal variation of crustal thickness from ~60 km beneath the Tethyan Himalaya to ~80 km beneath the Karakoram fault zone. A prominent intracrustal low velocity zone (IC-LVZ) is detected in the shear wave velocity models within the depth range ~15–40 km. The IC-LVZ identified at the stations both north and south of the ISZ can be interpreted as due to presence of fluid/partial melt. Our study provides compelling evidence that the mid-crustal low velocity zone does extend across the suture zone, in to the Tethyan Himalaya. The contact between this serpentinized ultramafic rocks and the eclogitized Indian continental crust in the suture zone is identified at ~47–50 km depth.

Description: The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P - and S -wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ~75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.

Description: Errors in the satellite orbits are considered to be a limitation for Interferometric Synthetic Aperture Radar (InSAR) time-series techniques to accurately measure long-wavelength (〉50 km) ground displacements. Here we examine how orbital errors propagate into relative InSAR line-of-sight velocity fields and evaluate the contribution of orbital errors to the InSAR uncertainty. We express the InSAR uncertainty due to the orbital errors in terms of the standard deviations of the velocity gradients in range and azimuth directions (range and azimuth uncertainties). The range uncertainty depends on the magnitude of the orbital errors, the number and time span of acquisitions. Using reported orbital uncertainties we find range uncertainties of less than 1.5 mm yr –1  100 km –1 for ERS, less than 0.5 mm yr –1  100 km –1 for Envisat and ~0.2 mm yr –1  100 km –1 for TerraSAR-X and Sentinel-1. Under a conservative scenario, we find azimuth uncertainties of better than 1.5 mm yr –1  100 km –1 for older satellites (ERS and Envisat) and better than 0.5 mm yr –1  100 km –1 for modern satellites (TerraSAR-X and Sentinel-1). We validate the expected uncertainties using LOS velocity fields obtained from Envisat SAR imagery. We find residual gradients of 0.8 mm yr –1  100 km –1 or less in range and of 0.95 mm yr –1  100 km –1 or less in azimuth direction, which fall within the 1 to 2 uncertainties. The InSAR uncertainties due to the orbital errors are significantly smaller than generally expected. This shows the potential of InSAR systems to constrain long-wavelength geodynamic processes, such as continent-scale deformation across entire plate boundary zones.

Description: A method for subsurface recognition of blind geological bodies is presented using combined surface constraints and 3-D structural modelling that incorporates constraints from detailed mapping, and potential-field inversion modelling. This method is applied to the Mount Painter Province and demonstrates that addition of low density material is required to reconcile the gravity signature of the region. This method may be an effective way to construct 3-D models in regions of excellent structural control, and can be used to assess the validity of surface structures with 3-D architecture. Combined geological and potential-field constrained inversion modelling of the Mount Painter Province was conducted to assess the validity of the geological models of the region. Magnetic susceptibility constrained stochastic property inversions indicates that the northeast to southwest structural trend of the relatively magnetic meta-sedimentary rocks of the Radium Creek Group in the Mount Painter Inlier is reconcilable with the similar, northeast to southwest trending positive magnetic anomalies in the region. Radium Creek Group packages are the major contributor of the total magnetic response of the region. However field mapping and the results of initial density constrained stochastic property inversion modelling do not correlate with a large residual negative gravity anomaly central to the region. Further density constrained inversion modelling indicates that an additional large body of relatively low density material is needed within the model space to account for this negative density anomaly. Through sensitivity analysis of multiple geometrical and varied potential-field property inversions, the best-fitting model records a reduction in gravity rms misfit from 21.9 to 1.69 mGal, representing a reduction from 56 to 4.5 per cent in respect to the total dynamic range of 37.5 mGal of the residual anomaly. This best-fitting model incorporates a volumetrically significant source body of interpreted felsic, low density material (10 12 m 3 ) impinging on the central-west of the Mount Painter Inlier and overlying Neoproterozoic sequences, and the emplacement of more mafic affinities in the northeast and east. The spatial association and circular geometry of these granitoid bodies suggests an affinity with the Palaeozoic ~460–440 Ma British Empire Granite that outcrops in the Mount Painter Inlier. The intrusion of this additional material in the Palaeozoic could either be the product of; or contributed to, an increased local geotherm and heat flow in the region during the Palaeozoic.

Description: The Pacific and Australian plates in the South Island, New Zealand (NZ) converge at a rate of about 4 cm yr –1 . Accommodation of the continental part of this convergence in the lithospheric mantle is both poorly understood and currently controversial yet it is a problem of fundamental importance for understanding lithospheric thickening. End-member possibilities range from the classical model of asymmetric subduction to symmetric viscous thickening. Seismic tomography has the potential to image this process. However, tomographic images to date are poorly constrained due to the lack of appropriate earthquakes. Improved teleseismic tomography of the region has been achieved by increasing data coverage and applying a novel scheme of correcting for crustal structure by ray tracing through a newly created model of shallow shear wave velocity derived from the inversion of noise-based dispersion measurements. Our resulting models suggest the lithospheric mantle high velocities at the continental plate boundary extend no deeper than approximately 125 km, evidence against both previous models of viscous drip and typical asymmetric subduction zones. This high velocity core extends from north to south along the axis of South Island suggesting that mantle convergence is accommodated along the older, mid-Cenozoic, plate boundary. West of South Island, a high velocity west dipping zone may define the remnant Cretaceous subduction zone that has been distorted by Cenozoic transcurrent deformation. We present our new 3-D seismic velocity models together with a compatible tectonic model and discuss their implications for the nature of lithospheric evolution at this convergent boundary.

Description: We use continuous GPS measurements from 31 stations in southern Mexico to model coseismic slip and post-seismic deformation from the 2012 March 20 M w  = 7.5 Ometepec earthquake, the first large thrust earthquake to occur below central Mexico during the modern GPS era. Coseismic offsets ranging from ~280 mm near the epicentre to 5 mm or less at sites far from the epicentre are fit best by a rupture focused between ~15 and 35 km depth, consistent with an independent seismological estimate. The corresponding geodetic moment of 1.4 10 20 N·m is within 10 per cent of two independent seismic estimates. Transient post-seismic motion recorded by GPS sites as far as 300 km from the rupture has a different horizontal deformation gradient and opposite sense of vertical motion than do the coseismic offsets. A forward model of viscoelastic relaxation as a result of our new coseismic slip solution incorrectly predicts uplift in areas where post-seismic subsidence was recorded and indicates that viscoelastic deformation was no more than a few per cent of the measured post-seismic deformation. The deformation within 6 months of the earthquake was thus strongly dominated by fault afterslip. The post-seismic GPS time-series are well fit as logarithmically decaying fault afterslip on an area of the subduction interface up to 10 times larger than the earthquake rupture zone, extending as far as 220 km inland. Afterslip had a cumulative geodetic moment of 2.0 10 20 N·m, ~40 per cent larger than the Ometepec earthquake. Tests for the shallow and deep limits for the afterslip require that it included much of the earthquake rupture zone as well as regions of the subduction interface where slow slip events and non-volcanic tremor have been recorded and areas even farther downdip on the flat interface. Widespread afterslip below much of central Mexico suggests that most of the nearly flat subduction interface in this region is conditionally stable and thus contributes measurable transient deformation to large areas of Mexico south of and in the volcanic belt.

Description: We have derived a shallow subsurface 2-D tomographic P -wave velocity image of the Deccan Volcanic Province (DVP) of India using first-arrival traveltime data along a 90-km-long N–S trending seismic profile in the Deccan Syneclise region. The tomographic image depicts smooth velocity variations of Quaternary and Tertiary (2.0–3.0 km s –1 ) sediments, basalts/traps (5.0–5.5 km s –1 ), sub-trappean Mesozoic sediments (4.3–4.5 km s –1 ) as well as the basement (5.9–6.1 km s –1 ) geometry down to a maximum depth of 5.0 km. Due to Late Cretaceous volcanism and outpouring of basaltic lava flows, this region is affected by numerous dyke intrusions and thick basaltic trap (2–3 km) exposed on the surface and surrounded by graben structures due to deep basinal faults forming a large igneous province. Although sub-basalt imaging is a major challenge for the oil industry, with the help of tomographic imaging technique of first-arrival seismic refraction data, we were able to image sub-trappean Mesozoic sediments (〈0.75 km) deposited below the two sequences of thick basaltic flows above the basement. The imaged Mesozoic sediments are expected to contain hydrocarbon because of their wide extension in this sedimentary basin with suitable trapping mechanism due to basalts. The robustness of the velocity image is assessed through numerous tests like velocity perturbations, 2 estimates, rms residuals of traveltime fit, uncertainty estimates through computation of ray-density or hits and series of checkerboard resolution tests with velocity anomalies having different cell size. The thickness of the basalt and the sub-trappean Mesozoic sediments along with the basement geometry obtained from tomography are constrained through ray-trace modelling and pre-stack depth migration (PSDM) of the wide-angle reflection phases for different shot gathers along the profile.

Description: Numerical experiments of convection with grain-damage are used to develop scaling laws for convective heat flow, mantle velocity and plate velocity across the stagnant lid and plate-tectonic regimes. Three main cases are presented in order of increasing complexity: a simple case wherein viscosity is only dependent on grain size, a case where viscosity depends on temperature and grain size, and finally a case where viscosity is temperature and grain size sensitive, and the grain-growth (or healing) is also temperature sensitive. In all cases, convection with grain-damage scales differently than Newtonian convection; whereas the Nusselt number (Nu), typically scales with the reference Rayleigh number, Ra 0 , to the 1/3 power, for grain-damage this exponent is larger because increasing Ra 0 also enhances damage. In addition, Nu, mantle velocity, and plate velocity are also functions of the damage to healing ratio, ( D / H ); increasing D / H increases Nu because more damage leads to more vigorous convection. For the fully realistic case, numerical results show stagnant lid convection, fully mobilized convection that resembles the temperature-independent viscosity case, and partially mobile or transitional convection, depending on D / H , Ra 0 , and the activation energies for viscosity and healing. Applying our scaling laws for the fully realistic case to Earth and Venus we demonstrate that increasing surface temperature dramatically decreases plate speed and heat flow, essentially shutting down plate tectonics, due to increased healing in lithospheric shear zones, as proposed previously. Contrary to many previous studies, the transitional regime between the stagnant lid and fully mobilized regimes is large, and the transition from stagnant lid to mobile convection is gradual and continuous. Thus planets could exhibit a full range of surface mobility, as opposed to the bimodal distribution of fully mobile lid planets and stagnant lid planets that is typically assumed.

Description: We measure impacts of liberalising European agriculture on farm income distribution in western Germany. Unlike previous studies, we do not treat market income and policy support as independent income sources. We jointly apply a partial equilibrium and a programming model and find that liberalisation increases inequality in relative terms though it decreases inequality in absolute terms. In particular, we analyse the relevance of taking into account policy-induced production and market responses in an ex-ante inequality analysis. We find that although their inclusion generally does not affect the direction of distributional effects, it may have considerable impact on their magnitude.

Description: In the past two decades, there has been an explosion of studies eliciting consumer willingness-to-pay for food attributes; however, this work has largely refrained from drawing a distinction between preferences for health, safety and quality on the one hand and consumers' subjective beliefs that the products studied possess these attributes, on the other. Using data from three experimental studies, along with structural economic models, we show that controlling for subjective beliefs can substantively alter the interpretation of results and the ultimate implications derived from a study. The results suggest the need to measure subjective beliefs in studies of consumer choice and to utilise the measures when making policy and marketing recommendations.

Description: Three magnetotelluric (MT) profiles in northwestern Canada cross the central and western segments of Great Slave Lake shear zone (GSLsz), a continental scale strike-slip structure active during the Slave-Rae collision in the Proterozoic. Dimensionality analysis indicates that (i) the resistivity structure is approximately 2-D with a geoelectric strike direction close to the dominant geological strike of N45°E and that (ii) electrical anisotropy may be present in the crust beneath the two southernmost profiles. Isotropic and anisotropic 2-D inversion and isotropic 3-D inversions show different resistivity structures on different segments of the shear zone. The GSLsz is imaged as a high resistivity zone (〉5000  m) that is at least 20 km wide and extends to a depth of at least 50 km on the northern profile. On the southern two profiles, the resistive zone is confined to the upper crust and pierces an east-dipping crustal conductor. Inversions show that this dipping conductor may be anisotropic, likely caused by conductive materials filling a network of fractures with a preferred spatial orientation. These conductive regions would have been disrupted by strike-slip, ductile deformation on the GSLsz that formed granulite to greenschist facies mylonite belts. The pre-dominantly granulite facies mylonites are resistive and explain why the GSLsz appears as a resistive structure piercing the east-dipping anisotropic layer. The absence of a dipping anisotropic/conductive layer on the northern MT profile, located on the central segment of the GSLsz, is consistent with the lack of subduction at this location as predicted by geological and tectonic models.

Description: We quantify the economic and health effects of a fruit and vegetable (F&V) voucher policy designed for increasing F&V consumption among low-income consumers. The analysis combined two models: an economic model which predicts how F&V consumption is affected by a change in policy, and a health model which evaluates the impact of a change in F&V consumption in terms of death avoided and life-years saved. We find that targeted F&V voucher policies can be more cost-effective than non-targeted policies based on tax decreases, but only when the targeted policy is focused narrowly on the lowest income consumers.

Description: The adoption of voluntary front-of-pack (FOP) nutrition labels by UK food retailers and manufacturers is explored. These labels highlight key nutrients, facilitating product comparisons. Information for 2,201 products launched between 2007 and 2009 was analysed. Binary and multinomial logistic regression models explore drivers of FOP label use. Products introduced more recently by retailers and certain food categories were more likely to carry FOP labels. Increasing the content of sodium and sugar decreased odds of FOP use in some categories, but with limited significance. Discussion includes policy options to optimise firm response and implications for evolving mandatory FOP labelling proposals.

Description: Using stated preference data from Kentucky and Ohio, USA, we estimate consumer willingness-to-pay for varieties of a processed food product (blackberry jam) that are differentiated with respect to their local production labelling and a series of other value-added claims. Results show that consumers were willing to pay more for the product indicating locally produced, produced in their state or in a well-identified multi-state region. Consumers were willing to purchase organic products, although there might be some confusion as to the meaning of the organic logo. Our results also supported the notion that consumers are willing to support small family farms.

Description: This paper studies the determinants and consequences of heterogeneous market participation among Polish dairy farmers using a unique data set on supply chain characteristics and individuals with different market relationships. It investigates factors that cause households not to participate in the market and then estimates farm orientation effects on revenues, using semi-parametric methods. The key finding is that farms maintaining commercial dairy business were better off than those who ceased milk sales. However, detailed analysis shows that this difference could be attributed to supply chain modernisation and becomes insignificant once subsistence farmers are compared to commercial farms supplying the traditional marketing channel.

Description: We develop a structural econometric model of the vertical contracts between soft drink manufacturers and retailers to assess the impact of taxes or changes in production costs on consumer prices. Using individual data on food purchases from a representative survey of 19,000 French households in 2005, we estimate consumer demand using a random utility approach. Among a set of possible vertical relationships, we select the model that best fits the data. We evaluate the pass-through rate of changes in input costs (sugar) or of taxes and show that the industry over-shifts cost changes or excise taxes to the consumers. This result challenges the belief that firms do not pass on the full extent of cost changes or excise taxes to consumers.

Description: India and China have the largest farm-household populations in the world—populations that are also among the poorest. Among the many factors that affect farm livelihoods, access to credit has been identified as a significant barrier preventing the escape from poverty. While there has been significant research on credit constraints in developing countries, there is surprisingly little information pertaining to the actual impacts of credit constraints on household well-being. The objective of this paper is to investigate the impacts of credit constraints on various factors affecting farm households, such as physical and human capital formation, agricultural inputs applications, consumption smoothing, and wage-seeking behavior using direct elicitation. This paper contributes to the literature and policy debates by comparing the effects of credit constraints in China and India as surveyed in 2008–2009. The analytical results and data demonstrate that binding credit constraints adversely affect a broad range of production and livelihood choices. We empirically show that credit constraints negatively affect food consumption, farm input applications, and health and educational attainments.

Description: There is broad debate about including agriculture in greenhouse gas (GHG) reduction efforts such as the European Emissions Trading Scheme. Since most agricultural GHG emissions originate from non-point sources, they cannot be directly measured, and therefore have to be derived by calculation schemes (indicators). We designed five such GHG indicators for dairy farms and analyzed the trade-offs between their feasibility, measurement accuracy, and level of induced abatement costs. Analyses of induced abatement costs and calculation accuracy are based on emission reduction simulations with a highly-detailed single-farm optimization model. Feasibility is discussed in a qualitative manner. Our results indicate that the trade-offs depend on both farm characteristics and the targeted reduction level. In particular, the advantages of detailed indicators decrease for higher abatement levels. Only the least feasible indicator led to abatement costs that would result in emission efforts at given prices in the European Emissions Trading Scheme, although with a rather small potential. Our results thus suggest little potential for including dairy production into market-based reduction policies.