ALBERT

Notes: Reimbursement systems for health-care providers are very complex, like the production systems that they regulate. This complexity has led to some important misperceptions about the incentive consequences of major reimbursement reforms. One example is the prospective payment system (PPS), developed to provide “high-powered” incentives through fixed prices for hospital admissions for the US elderly. In fact, various features of the DRG system allow reimbursement to vary with actual treatment decisions during an admission, and so are not prospective. This paper develops a general method for measuring actual reimbursement incentives in complex regulated price systems. The method uses regression techniques with variance decompositions to quantify the effects of particular features of the payment system on prospective and retrospective cost sharing, as well as overall generosity of payments. I apply this method to microdata on 20 percent of Medicare hospital admissions in 1987 and 1990 to summarize the incentives created by PPS in practice, and how the incentives are evolving over time. I show that PPS involves limited and decreasing cost sharing with hospitals, most of which is not prospective. The reimbursement incentives vary substantially across diagnoses, demographic groups, and types of intensive treatments, possibly with important implications for hospital behavior and medical expenditure growth. The techniques developed here can be used to analyze a broad range of provider reimbursement mechanisms.

Notes: In a health insurance market, a large employer or an organized “buyer alliance” is in a position to influence the design of plans offered to its members. We study how the sponsors of buyer alliances manage competition among insurance firms by focusing on their choices of the format of competition, the number of firms allowed to compete, and the quality of care offered by the firms. We find deviations from optimality in all three dimensions. Specifically, we find a tendency toward too many firms and too much quality, and a bias toward a format involving the prescreening of insurance plans by the sponsor.

Notes: This paper empirically examines the effect of firm-specific characteristics on the length of time required by the Food and Drug Administration (FDA) to review and approve new-drug applications between 1990 and 1992. The approach treats regulatory decisions as endogenous and explains the variation in regulatory behavior as a function of differences that exist between firms and drugs. Results show that, controlling for drug-specific characteristics, regulators respond to firm-specific characteristics when evaluating new drug applications. For instance, firms that are less diversified and more R&D-inten-sive receive shorter review times for their new-drug applications than more diversified and less R&D-intensive firms. The reason is that most firm characteristics signal information to reviewers about either firm reputation or application quality. This information reduces reviewers' uncertainty about approving a dangerous or ineffective drug and leads to faster review times. The results suggest that regulators respond to the heterogeneities among firms in the pharmaceutical market in systematic ways.

Notes: I examine the outcomes of cases of entry by merchant shipping lines into established markets around the turn of the century. These established markets are completely dominated by an incumbent cartel composed of several member shipping lines. The cartel makes the decision whether or not to begin a price war against the entrant; some entrants are formally admitted to the cartel without any conflict. I use characteristics of the entrant to predict whether or not the entrant will encounter a price war conditional on entering. I find that weaker entrants are fought, where “weaker” means having fewer financial resources, less experience, smaller size, or poor trade conditions. The empirical results provide most support for the long-purse theory of predation. Due to the small number of observations available, 47, I discuss qualitative evidence (such as predatory intent expressed in correspondence between cartel members) that supports the empirical results. The results are also found to be robust to misclassification of the dependent variable, which is a particular concern when dealing with historical data.

Notes: The paper analyzes tender offers and proxy contests as alternative means of resolving corporate governance conflicts between dissidents and incumbent management. We show that when a dissident shareholder is sufficiently confident about the potential benefits from changing corporate policy, he will seek majority control by making a tender offer rather than initiating a proxy contest. When the dissident is relatively uninformed, however, he may opt for a proxy contest, thereby utilizing the information of other shareholders to implement the better policy. Consistent with empirical evidence, the model predicts that announcements of tender offers will tend to be associated with larger positive stockprice reactions than announcements of proxy contests. The model is easily extended to allow for promanagement bias in proxy voting by institutional investors. Empirical observations that have been viewed as evidence of such promanagement bias are shown to be quite consistent with the absence of such bias. Policy issues are discussed as well. An interesting result is that even policies targeted at reducing the costs of conducting proxy contests may have ambiguous social consequences, given the possibility of substitution between tender offers and proxy contests.

Notes: This article investigates the issue ofpredation by a regulated firm. Since it has private information, a regulated firm obtains higher rents in case of successful predation: the fewer the competitors, the higher the marginal social value of the regulated firm's effort and the higher the informational rents. Both principals (the investor of a “target” firm and the regulator) have to provide some incentives to prevent predation: the investor has to reduce the sensitivity of refinancing to predation; the regulator has to lower the gain of successful predation. It is shown that there is a trade-off between the power of the regulatory incentive scheme and the regulated firm's incentives to prey. In addition, as deterring predation is costly, the investor and the regulator compete when offering contracts: each wants to free-ride on the other. Hence, predation may occur in equilibrium although it makes both principals worse off.

Notes: This paper studies the nature of incentive contracts between a risk-neutral principal and a risk-neutral agent under the constraint that the agent's liability is limited. A necessary and sufficient condition is derived for the existence of a first-best contract under this constraint, and a bonus-based contract is shown to be the most efficient contractual form. Implications of bonus contracts are also discussed.

Notes: This paper examines the effect of the MFC rules adopted by Medicaid on both price dispersion and price levels in the wholesale pharmaceutical market. Theory suggests that the regulations should reduce price dispersion and increase the average price for those products with a high initial level of price dispersion. Using data which can only measure some dimensions of price discrimination, I find that discrimination falls for products sold to hospitals, but not drugstores. Branded drugs facing generic competition have the most dispersion ex ante. Prices of these brands rise with dispersion at the implementation of the new rules. The last two results are consistent with Scott Morton (1997), where I look only at price changes due to the law. The results of this paper confirm that part of the mechanism of action for the price increase is the high level of price dispersion for some products combined with the MFC.

Notes: This paper examines the incentive effects of division of labor on worker effort, in the absence of the scale effects studied by Adam Smith. The game-theoretic model gives two results. (1) Suppose workers are identical and risk-neutral, and there is stochastic observation of group output by the firm offering compensations subject to some worker-participation constraint. Then the firm can arrive at the same first-best outcome with or without division of labor. However, if workers are risk-averse, division of labor can give the firm strictly greater profit. (2) A deepening division of labor magnifies this positive incentive effect; but if workers are heterogeneous, or if there are certain informational imperfections in the production process, this incentive advantage of division of labor could be impaired or even reversed. The first result may help explain the emergence of division of labor in the early stages of industrialization without relying on the Smithian advantages, which are also present in some labor deployment schemes without division of labor. The second result throws light on some recent anecdotal evidence of a shallowing division of labor in some areas of modern manufacturing. These factors affecting the efficiency of division of labor are then further discussed in the light of recent empirical findings on division of labor and team work, such as those in Katzenbach and Smith (1993).

Notes: We show how technological flexibility choices and equilibrium configurations (both simultaneous and sequential duopoly) depend on six industry characteristics. Low market volatility combined with intermediate market size favors inflexible technologies; large values of either volatility or size favor flexible technologies; low or intermediate values of both favor the coexistence of flexible and inflexible technologies. The possibility of a flexibility trap exists in industries of low volatility and intermediate size. Entry prevention can sometimes be achieved by inflexible technologies or flexible technologies, depending on the industry characteristics.

Notes: We examine how the feasibility of both nonlinear pricing and exclusive dealing arrangements affect incentives for market foreclosure when two manufacturers contract with a retail monopolist. Surprisingly, we find that although market foreclosure equilibria exist, they are Pareto-dominated (from each manufacturer's perspective) by all nonforeclosure equilibria. If one believes that Pareto-dominated equilibria are unlikely to arise, then the difference between our results and those of Mathewson and Winter (1987), who do not allow for nonlinear pricing, suggests an ironic twist on the notion that quantity discounts and other kinds of nonlinear pricing can provide an additional way for a manufacturer to foreclose a rival. By providing a manufacturer with increased flexibility (beyond linear pricing) to extract a retailer's surplus, nonlinear pricing may instead have the effect of reducing the incidence of observed market foreclosure.

Notes: A model of vertical integration is studied. Upstream firms sell differentiated inputs; downstream firms bundle them to make final products. Downstream products are sold as option contracts, which allow consumers to choose from a set of commodities at predetermined prices. The model is illustrated by examples in telecommunication and health markets. Equilibria of the integration game must result in upstream input foreclosure and downstream monopolization. Consumers may or may not benefit from integration.

Notes: This paper discusses the regulation of oligopolistic differentiated-product industries. The regulator can control prices and impose quantity restrictions, but cannot control the quality choices of the firms. We inquire about the optimal choice of regulatory regime—whether and under what conditions managed competition or segmentation of the market between regulated monopolies achieves better results. In the spatial duopoly model analyzed here, unhindered competition generally results in an inefficient allocation. When the regulator knows the technologies, optimal managed competition results in distortions of the quality choice, but an optimal regulated-monopolies regime achieves the first best outcome. When the regulator is uncertain about the technologies, neither of these methods yields the first-best outcome. The regulated-monopolies regime still tends to produce better quality choices, but managed competition tends to be more effective at extracting rents from the firms. The overall comparison depends on some finer details of the environment.

Notes: This paper studies the business practice of offering discounts to new customers in markets with switching costs. In a two-period homogeneous-good duopoly model, it is shown that the equilibrium amount of discounts increases continuously in the expected switching costs of a typical consumer. In equilibrium, firms offer the same prices and discounts in a mature market even if they have different market shares, and the demands faced by these firms in a new market become more elastic. Firms are worse off engaging in the discriminatory pricing, while consumers need not necessarily benefit from it. There is costly equilibrium switching of consumers, which creates a dead-weight loss to the society.

Notes: This paper analyzes six spectrum auctions conducted by the Federal Communications Commission from July 1994 to May 1996. These auctions were simultaneous multiple-round auctions in which collections of licenses were auctioned simultaneously. This auction form proved remarkably successful. Similar items sold for similar prices, and bidders successfully formed efficient aggregations of licenses. Bidding behavior differed substantially in the auctions. The extent of bidder competition and price uncertainty played an important role in determining behavior. Bidding credits and installment payments also played a major role in several of the auctions.

Notes: We examine bid data from the first two broadband PCS spectrum auctions for evidence of value synergies. First, we estimate a benchmark regression for the determinants of final auction prices. Then, we include variables reflecting the extent to which bidders ultimately won or already owned the adjacent wireless properties. Consistent with geographic synergies in an ascending-bid auction, prices were higher when the highest losing bidder had adjacent licenses. The footprints of winning bidders suggest that they were often successful in realizing these synergies.

Notes: When multiple items are sold through the use of simultaneous ascending-bid auctions, bidders can find it in their mutual interests to reduce their aggregate demand for the items while prices are still low relative to the bidders' valuations. The FCC's first broadband PCS auction provides examples of how such mutual reductions might be arranged even when the bidders are not allowed to communicate with one another outside of the auction arena.

Notes: In late 1994, GTE, one of the largest telecommunications firms in the world, entered an auction for the rights to provide personal communications services (PCS) using the electromagnetic spectrum. The administering agency, the Federal Communications Commission, adopted a novel multiple-round format for the PCS auction. The format presented GTE with a complex bidding problem. This article describes how the GTE bidding team answered the following question: Given its budget and valuations and the information available about rival bidders, how should GTE bid to achieve the best attainable outcome?

Notes: The paper reviews the uses of laboratory experimental economics methods in the background research and implementation of the Personal Communication Systems auctions held by the Federal Communications Commission. The applications began during the rule making process with the testing of broad rules that might be implemented. Data from experiments were systematically used. The methods were used again in the software development process where several important contributions were made. Finally, experiences gained from the study of experimental auction processes were used in the actual management of the first auctions and in interpreting auction performance.

Notes: A series of two-player, second-price common-value auctions are reported. In symmetric auctions, bidders suffer from a winner's curse. In asymmetric auctions in which one bidder has a private value advantage, the effect on bids and prices is proportional rather than explosive (the prediction of Nash equilibrium bidding theory). Although advantaged bidders are close to making best responses to disadvantaged bidders, the latter bid much more aggressively than in equilibrium, thereby earning negative average profits. Experienced bidders consistently bid closer to the Nash equilibrium than inexperienced bidders, although these adjustments towards equilibrium are small and at times uneven.

Notes: This paper reports the results of over 130 auctions conducted under controlled conditions to examine the robustness of several auction mechanisms to allocate multiple objects. The simultaneous discrete auction process used by the Federal Communications Commission to allocate Personal Communications licenses was contrasted with a sequential auction and a combinatorial auction over a variety of demand conditions. In test environments created to check only the minimum competency of the procedures, the simultaneous discrete auction process produces highly efficient allocations, approaching levels similar to those found with a continuous form of the auction, and it outperforms a sequential auction. However, in environments created to stress test the procedures, a combinatorial auction outperforms the simultaneous discrete auction.

Notes: The firm is often considered as a nexus of contracts linking the management and its different stakeholders: claim-holders, workers, unions, customers, suppliers, and the state, among others. This paper surveys recent work in contract theory, the multiprincipal incentive theory, and the theory of side contracts, which provides some insights into the structure of those contracts and therefore into the structure of the firm. First, we discuss the incomplete contracting assumptions underlying these variations of the usual grand contract approach. Second, we explain how the theoretical lessons learned from this work—the distribution of contracting rights, the power of incentive schemes within organizations, and the design of communication channels—apply to the theory of the firm.

Notes: We present a dynamic model of the hospital industry in which nonprofit and for-profit hospitals coexist and compete and are differentiated by their objective functions, investment technologies, and taxation rates. In our model, patients differ by income and type of insurance coverage, and choose admission to their preferred hospital, while hospitals choose investment, entry, exit, and pricing strategies. We estimate the parameters of the model with aggregate data and a GMM procedure. We then use the model to examine the effects of changes in the Medicare reimbursement system, universal health-care coverage, and taxation of nonprofits.

Notes: We have demonstrated that when providers of health insurance are perceived to be differentiated by consumers, circumstances may arise under which they find it advantageous to restrict the set of health-care providers that they approve to their customers. Even if all health-care providers are equally qualified and efficient, payers may choose to contract with a selected subset of them in order to secure more favorable contract terms. Moreover, in a concentrated health-care market that consists of two health insurance companies (payers) and two health-care providers (hospitals), both payers may choose to contract with only one of the hospitals while excluding the other completely from the market. When consumers' valuation of an extended choice of providers is small in comparison with the extent of differentiation that exists between the payers, such an exclusionary outcome is the unique equilibrium of the game.

Notes: During the 1980s the share of prescriptions sold by retail pharmacies that was accounted for by generic products roughly doubled. The price response to generic entry of brand-name products has been a source of controversy. In this paper we estimate models of price responses to generic entry in the market for brand-name and generic drugs. We study a sample of 32 drugs that lost patent protection during the early to mid-1980s. Our results provide evidence that brand-name prices increase after generic entry and are accompanied by large decreases in the price of generic drugs.

Notes: We develop a model of competition among health maintenance organizations (HMOs) to analyze the effects of market power, scale economies, and asymmetric knowledge of health risk on market outcomes. We find that competition among HMOs may, but need not, ensure socially preferred outcomes. Market power or scale economies can sometimes admit socially preferred outcomes when they would otherwise not arise. Asymmetric knowledge of health risk may or may not be constraining. When it is constraining, a variety of patterns of incomplete health insurance can arise, along with excessive or insufficient treatment and preventive care for either high-risk or low-risk individuals.

Notes: This paper surveys recent work in contract theory that relates to the allocation of tasks among agents within an organization as well as to the effect of product market competition upon optimal contracting and agency costs.

Notes: In settings where the revelation principle applies, delegation arrangements are frequently inferior to centralized decision making, and at best achieve the same level of performance. This paper studies the value of delegation when organizations are constrained by a bound on the number of contingencies in any contract. For a principal-agent setting with asymmetric information, we compare centralized mechanisms where the principal retains sole responsibility for contracting and coordinating production, with delegation mechanisms where one agent (a manager) is delegated authority to contract with other agents and coordinate production. Relative to centralization, delegation entails a control loss, but allows decisions to be more sensitive to the manager's private information. We identify circumstances under which the flexibility gain outweighs the control loss, so that delegation emerges superior to centralized contracting.

Notes: This paper examines the integration of market and nonmarket strategies in a setting involving market competition and international trade policy where governments serve as bargaining agents for firms. In the case modeled, the Eastman Kodak Company (Kodak) filed a Section 301 petition under US trade law against practices of Fuji Photo Film Company (Fujifilm) in the Japanese distribution system that Kodak alleges constitute trade barriers. The model has four components. The market model characterizes the competition between Fujifilm and Kodak, incorporating characteristics descriptive of the demand and market structure in Japan. Enforcement of an international trade agreement focusing on practices in a distribution system are problematic, so the second model characterizes the sustainability of concessions obtained through a trade agreement using a repeated game extension of the market model. The third model characterizes the bargaining between the US and Japanese governments using the preferences induced by the market model and the limits on sustainable concessions characterized in the second model. Using a common-agency framework, the fourth model represents the nonmarket competition between the two firms as they work to influence the bargaining positions of the governments. The result is a model in which market and nonmarket strategies are integrated in a formal theory of the resolution of trade disputes and the subsequent effects on market competition. The equilibrium characterized allows a comparative statics analysis of the synergies between market and nonmarket strategies.

Notes: This article investigates the issue of predation by a regulated firm. Since it has private information, a regulated firm obtains higher rents in case of successful predation: the fewer the competitors, the higher the marginal social value of the regulated firm's effort and the higher the informational rents. Both principals (the investor of a “target” firm and the regulator) have to provide some incentives to prevent predation: the investor has to reduce the sensitivity of refinancing to predation; the regulator has to lower the gain of successful predation. It is shown that there is a trade-off between the power of the regulatory incentive scheme and the regulated firm's incentives to prey. In addition, as deterring predation is costly, the investor and the regulator compete when offering contracts: each wants to free-ride on the other. Hence, predation may occur in equilibrium although it makes both principals worse off.

Notes: Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.

Notes: Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.

Notes: Book reviewed in this article: Human impact on Erosion and Sedimentation By D. E. Walling & J.-L. Probst (editors).

Notes: Book reviewed in this article: Soil erosion by water in Africa: Principles, Prediction and Protection By D. Nill, U. Schwertmann, U. Sabel-Koscella, M. Bernhard & J. Breuer.

Notes: Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil-K and the velocity constants for fixation and release of soil-K, can be readily measured by a novel procedure which is described.The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed-K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop-K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.A simplified version of the model runs interactively on the Internet at:

Notes: Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring-applied N-fertilizer are studied. The immobilization of 15N-labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum 〉 1200 no longer caused appreciable immobilization of spring fertilizer.

Notes: Book reviewed in this article: Erosion and sediment yield: global and regional perspectives Edited by D. E. Walling and B. W. Webb.

Notes: Abstract. The restorative ability of herbaceous (Psophocarpus palustris, Pueraria phaseoloides) and woody (Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis, test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.

Notes: Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small (c. 1.5 m2) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.

Notes: The UK government recently introduced legislation to treat the qualifying distribution on a repurchase of shares in the same way as ‘foreign income dividends’. This paper examines and criticises this reform from two perspectives. First, there is no underlying rationale for such an approach. Second, the legislation moves the tax system away from simplification. A better approach would have been to remove the advance corporation tax (ACT) charge on a repurchase. JEL classification: H25, K34.

Notes: This paper examines the impact of the UK housing benefit system on the financial returns to employment of people in local authority or Housing Association accommodation. It outlines the current structure of housing benefit and examines its effects on the returns to employment using data from the Family Expenditure Survey. It analyses the consequences of a number of reforms to the current system — lowering social rents, increasing the levels of housing benefit received in work and restricting the amount of rent covered by housing benefit payments. This analysis highlights the trade-offs involved in various strategies available for restructuring the present system. JEL classification: H3, H4, J3.

Notes: Abstract. The effect of superficial liming of acidic forest soils on CO2 and N2O emissions and CH4 uptake was investigated with closed chambers in two deciduous and two spruce forests, by weekly to biweekly measurements over at least one year. The flux rates of untreated areas varied between 1.94 and 4.38 t CO2-C/ha per y, 0.28 and 2.15 kg/N2O-N/ha per y and between 0.15 and 1.06 kg CH4-C/ha per y. Liming had no clear effect on CO2 emissions which may change in the long-term with decreasing root turnover and increasing C-mineralization. Apart from one exception, liming resulted in a reduction of N2O emissions by 9 to 62% and in an increase of CH4 uptake by 26 to 580%. The variability in N2O emissions between the forest sites could not be explained. In contrast, the variability of annual CH4 uptake rates could be explained by N content (r2= 0.82), C content (r2= 0.77), bulk density (r2= 60), pore space (r2= 0.59) and pH (r2= 0.40) of mineral soil at a depth of 0 to 10 cm, and by the quantity of material in the organic layer (r2= 0.66). Experiments with undisturbed columns of the same soils showed that between 1 and 73% of the total N2O emissions came from the organic layer. However, atmospheric CH4 was not oxidized in this layer, which represents a diffusion barrier for atmospheric CH4. When this barrier was removed, CH4 uptake by the mineral soil increased by 25 to 171%. These results suggest that liming of acidic forest soils causes a reduction of the greenhouse gases N2O and CH4 in the atmosphere, due to changes in the chemical, biological, and physical condition of the soils.

Notes: Abstract. Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors.In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration.In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere.Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments.By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.

Notes: Abstract. Field measurement of landfill methane (CH4) emissions indicates natural variability spanning more than seven orders of magnitude, from less than 0.0004 to more than 4000 g/m2 per day. This wide range reflects net emissions resulting from production (methanogenesis), consumption (methanotrophic oxidation), and gaseous transport processes. The determination of an ‘average’ emission rate for a given field site requires sampling designs and statistical techniques which consider spatial and temporal variability. Moreover, particularly at sites with pumped gas recovery systems, it is possible for methanotrophic microorganisms in aerated cover soils to oxidize all of the CH4 from landfill sources below and, additionally, to oxidize CH4 diffusing into cover soils from atmospheric sources above. In such cases, a reversed soil gas concentration gradient is observed in shallow cover soils, indicating bidirectional diffusional transport to the depth of optimum CH4 oxidation. Rates of landfill CH4 oxidation from field and laboratory incubation studies range up to 166 g/m2 per day, among the highest for any natural setting, providing an effective natural control on net emissions. It has been shown that methanotrophs in landfill soils can adapt rapidly to elevated CH4 concentrations with increased rates of CH4 oxidation related to depth of oxygen penetration, soil moisture, and the nutrient status of the soil.Estimates of worldwide landfill CH4 emissions to the atmosphere have ranged from 9 to 70 Tg/y, differing mainly in assumed CH4 yields from estimated quantities of landfilled refuse. At highly controlled landfill sites in developed countries, landfill CH4 is often collected via vertical wells or horizontal collectors. Recovery of landfill CH4 through engineered systems can provide both environmental and energy benefits by mitigating subsurface migration, reducing surface emissions, and providing an alternative energy resource for industrial boiler use, on-site electrical generation, or upgrading to a substitute natural gas. Manipulation of landfill cover soils to maximize their oxidation potential could provide a complementary strategy for controlling CH4 emissions, particularly at older sites where the CH4 concentration in landfill gas is too low for energy recovery or flaring. For the future, it is necessary to better quantify net emissions relative to rates of CH4 production, oxidation, and transport. Field measurements, manipulative studies, and model development are currently underway at various spatial scales in several countries

Notes: Book Reviewed in this article: Phosphorus loss from soil to water: Edited by H. Tunney, O. T. Carton, P. C.

Notes: Abstract. Variously timed sub-optimal irrigation strategies were applied to sugarbeet grown on a light soil (loamy sand or sandy loam) over four seasons (1991 to 1994) to investigate the effect on crop growth and nitrate leaching risk. Data from the two dry seasons, (1991 and 1994) are reported here. In the driest year (1991) soil mineral N levels after autumn harvest were negatively related to crop water use (P 〈 0.05). In this season, there was little drainage from the soil profile, and full irrigation reduced residual soil N by 31 kg N/ha (0-90 cm) compared with the unirrigated treatment (79 kg N/ha). The potential for N leaching during the ensuing winter was consequently more than halved. In 1991 and 1994 there was a strong positive linear relationship between dry matter yield, N uptake and water use, but a negative relationship between plant N concentration and water use. These relationships were a function of the severity and not the timing of drought. The additional N uptake associated with increased irrigation and crop water use was biased towards a large concentration in the aboveground crop (tops), which are normally returned to the soil. The C:N ratio of sugarbeet tops was affected by crop water supply with droughted crops having lower values. This would also influence N release and subsequent leaching risk. However, the effects of drought on N leaching risk were relatively small when compared with other root crops such as potatoes.

Notes: Abstract. The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides, and silver birch, Betula pendula, and the ley crops were one to five years old.The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops.Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.

Notes: Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO4-P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO4-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.

Notes: Book Reviewed in this article: Freshwater Contamination By B. Webb (editor).

Notes: Book Reviewed in this article: Biotechnical and soil bioengineering slope stabilization. A practical guide for erosion control By D. H. Gray & R. B. Sotir.

Notes: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.

Notes: Abstract. Nitrate leaching after one year of a cut grass/clover ley was measured in two succeeding years to investigate how the postponing of ploughing leys from early to late autumn or spring, in combination with spring or winter cereals affected leaching of nitrate. The experiment was conducted as three field trials, two on a coarse sandy soil and one on a sandy loam soil. For calculation of nitrate leaching, soil water samples were taken using ceramic suction cups. The experiments started in spring in a first year ley and ended in spring three years later. Total nitrate leaching for the three year periods for each trial ranged between 160–254 and 189–254 kg N/ha on the coarse sand and 129–233 kg N/ha on the sandy loam. The results showed that winter wheat (Triticum aestivum L.) did not have the potential for taking up the mineralized N in autumn after early autumn ploughing of grass/clover leys, and that the least leaching was generally found when ploughing was postponed until spring, and when winter rye (Secale cereale L.) was grown as the second crop rather than spring barley (Hordeum vulgare L.). Nevertheless, leaching was generally high in the winter period even when winter rye was grown. On these soil types ploughing out should be postponed, whenever possible, to spring. Crop systems that maximize the utilization of mineralized N and thereby minimize nitrate leaching need to be further developed. Based on N balances, the data were further used to estimate the biological N fixation by the clover.

Notes: Abstract. Ceramic suction cups were used to obtain samples of soil solution from permanently grazed swards receiving 200 kg N/ha/y. The suction cups were installed in 1 ha plots at 10, 30 and 60 an depth in a poorly drained, heavy clay soil in S. W. England. The plots were hydrologically isolated from each other by perimeter drains which channelled surface runoff water into v-notch weirs. In one treatment, artificial drainage by a system of field and mole drains also converged to outfalls through v-notch weirs, which enabled samples to be taken. Nitrate and a range of other ionic constituents were examined over a 12 month period in soil solutions taken from the suction cups and compared with leachate obtained from the field drains and surface channels. Field drain samples frequently exceeded the EC limit of 11.3 mg nitrate-N/1, but concentrations in suction cups obtained during the same period did not, and were up to ten-fold less. Although correlations for ions were found between different sampling depths and drainage samples, no clear patterns emerged. It was concluded that suction cups were inappropriate for the determination of the overall leaching losses in this soil type, but provided useful data on changes in ionic concentrations which occurred in different soil horizons through to drainage outfalls.

Notes: Abstract. The impact of soil erosion on soil productivity was estimated for a Rhodic Ferralsol and a Eutric Cambisol in Santa Catarina, southern Brazil. Over equivalent periods, total soil losses were an order of magnitude different (868 and 68 t/ha respectively on the bare soil control), yet the impact on maize yield per tonne of soil lost was far greater at the Cambisol site with less erosion. Similar interesting contrasts between sites were found for the other measures of impact with decline in pH and phosphorus and increase in free aluminium being the most obvious induced soil differences. The results demonstrate the variable nature of erosion impact according to soil type and they highlight the importance of examining a number of measures of impact before pronouncing on the sustainability of any particular agricultural practice.

Notes: Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca2+ (down to 0.01 cmolc/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus-one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm3/cm3) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.

Notes: Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies.

Notes: Abstract. Soil salinity and alkalinity reduce plant production and alter species composition of meadow grasslands in western Jilin Province, China. This study was designed to compare the survival and growth of three grass species (Aneumlepidium chinense, Puccinellia tenuijlora and Hordeum brevisubulatum) transplanted into saline-alkali soils in the field, and to evaluate the effects of gypsum amendments on soil properties and growth of these species. Gypsum treatments decreased soil pH, electrical conductivity, and chloride and sodium levels; water infiltration and calcium levels were increased. Survival of grass transplants was increased by gypsum treatments. Tiller number and height, and grass yields were all increased by the application of gypsum. Improvements in plant growth and survival with gypsum treatment appeared to be due to reduced chloride levels and increased Ca availability in the soil, and to changes in soil structure leading to improved infiltration rates. Revegetation of salinelalkaline soils in this region would be improved by application of gypsum in the range of 14–19 t/ha.

Notes: The charitable giving of UK households has changed considerably over the past 20 years. In particular, the proportion of households giving to charity fell by 5 percentage points between 1974 and 1993–94. An increase in the average size of donations meant that total voluntary income increased in real terms over the period, but, since 1988, voluntary income has stagnated. The greatest falls in the number of givers are among households in their twenties and thirties. There are clear trends in giving across households by age and income, with younger and poorer households tending to give less. But not only are today's younger households less likely to give than today's middle-aged households; they are also less likely to give than today's middle-aged households did when they were young. These generational trends in giving do not bode well for levels of voluntary income in the future. JEL classification: D12. D16.

Notes: The tax system in the UK has developed through numerous ad hoc changes to its structure. This has resulted in a situation where the way in which the tax system is described does not readily correspond to the marginal rate schedule actually faced by taxpayers. This paper outlines the connection between the formal description of the tax system and the marginal rate schedule faced by taxpayers. It argues that the operation of the tax system would be greatly clarified if it were described explicitly in terms of its marginal rate schedule.

Notes: This paper considers some of the economic impacts that demographic change may have in developed economies over the next fifty years. I focus on the role that financial markets might play in economies where the pressure on government-run unfunded pension systems is likely to rise. The role of unfunded schemes is considered in a world where financial markets are incomplete and important types of risk cannot easily be offset by trading. How demographic shifts might affect labour productivity, asset prices and aggregate output is investigated using a simulation model of an economy where population structure is changing. JEL classification: E21, E60, G10, H1.

Notes: The ‘Green Book’ and the recent EGRUP report support exchequer cost per job as a key input in the ex-ante appraisal of individual applications for Regional Selective Assistance (RSA) and the ex-post evaluation of the RSA scheme as a whole. In this paper, following a recommendation in the House of Commons Trade and Industry Committee's report on regional policy, the merits of an alternative, explicitly cost-benefit, framework are outlined. This approach incorporates the administration and compliance costs of the subsidy, costs at present ignored in RSA evaluation studies. An optimal ex-ante appraisal rule is developed. This takes the form of a cost-per-job ceiling, and a representative value is calculated for this figure. JEL classification: H20.

Notes: Abstract. Methane (CH4) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH4; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH4 emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade-offs that are possible, have still to be identified.

Notes: Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land-use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.

Notes: Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N2O budget. This paper summarizes relevant literature data on N2O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N2O budget.The effects of grazing animals on N2O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N2O. There are no pertinent data about the effects of compaction by treading cattle on N2O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N2O-N per year. This is slightly more than 10% of the global budget.

Notes: Abstract. Increases in the atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and to ozone depletion in the stratosphere. Nitric oxide (NO) is a cause of acid rain and tropospheric ozone. The use of N fertilizers in agriculture has direct and indirect effects on the emissions of both these gases, which are the result of microbial nitrification and denitrification in the soil, and which are controlled principally by soil water and mineral N contents, temperature and labile organic matter.The global emission of N2O from cultivated land is now estimated at 3.5 TgN annually, of which 1.5 Tg has been directly attributed to synthetic N fertilizers, out of a total quantity applied in 1990 of about 77Tg N. This amount was 150% above the 1970 figure. The total fertilizer-induced emissions of NO are somewhere in the range 0.5-5 Tg N. Mineral N fertilizers can also be indirect as well as direct sources of N2O and NO emissions, via deposition of volatilized NH3 on natural ecosystems and denitrification of leached nitrate in subsoils, waters and sediments.IPCC currently assume an N2O emission factor of 1.25 ± 1.0% of fertilizer N applied. No allowance is made for different fertilizer types, on the basis that soil management and cropping systems, and unpredictable rainfall inputs, are more important variables. However, recent results show substantial reductions in emissions from grassland by matching fertilizer type to environmental conditions, and in arable systems by using controlled release fertilizers and nitrification inhibitors. Also, better timing and placement of N, application of the minimum amount of N to achieve satisfactory yield, and optimization of soil physical conditions, particularly avoidance of excessive wetness and compaction, would be expected to reduce the average emission factor for N2O. Some of these adjustments would also reduce NO emissions. However, increasing global fertilizer use is likely to cause an upward trend in total emissions even if these mitigating practices become widely adopted.

Notes: Abstract. The validity of the model described in Greenwood & Karpinets (1997) was tested against the results of single year, multi level K fertilizer experiments. Measurements of plant mass, %K in the plant and K activity ratio in soil had been made at harvest and at intervals during the growing season on spring wheat, summer cabbage and turnips. Reasonably good agreement was obtained between these measurements and simulated values when the two ‘crop’ parameters (defining the dependence of critical and maximum possible %K on plant mass) were adjusted for each crop. Also good agreement was generally obtained for plant weight and plant %K at harvest in less detailed experiments on 10 other crops. Values of the two ‘crop’ parameters for 12 of the crops were strongly correlated with one another suggesting that a single ‘crop’ parameter may be all that is required to define most inter-species differences in plant-K demand.Simulations with the model indicate that, in central England, no response of 10 crops to K fertilizer would be likely on soils containing more than 170 mg of 1 M ammonium nitrate extractable-K/kg of soil and having clay contents of between 15 and 45%. Shortcomings of the model and opportunities for advance are discussed.A simplified version of the model runs on the Internet at:

Notes: Abstract. As part of a study of recession farming on the ‘fadama’ lands on a segment of the Komadugu-Yobe floodplain, a survey was carried out to investigate the local farmers’ perception of soil types and management practices. The farmers are clearly aware of the differences in soil type on the fadama and they possess unique skills in managing their farm lands. The farmers classify fadama soils for recession farming by assessing soil texture and soil drainage conditions by feel and observation. Integrating such local knowledge into soil surveys will lead to better practical definition of mapping units and give soil names that have more meaning for the farmers.

Notes: Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

Notes: Abstract. The projected increase in sewage sludge used on land within many countries in the European Community will provide a major source of entry for several heavy metals into the soil. Although the application rate of sewage sludge to agricultural land is constrained by maximum annual additions of heavy metals, there is a need to know the sensitivity of those soils to heavy metal inputs which are physically suited for application. A rulebased classification using weighted parameters designed to assess the metal binding capacity of soil and the risk of groundwater pollution has been applied to soils data held within the Macaulay Land Use Research Institute's National Soils Inventory The classification uses soil pH, organic matter content, texture and soil colour as a surrogate for iron oxide concentration. The results indicate that some metals, for example cadmium and zinc are potentially more mobile in soils than others such as lead, but that the majority of soils display a strong or very strong binding capacity for all the metals. However this pattern can only be sustained if the soil pH values are maintained at their present values; a fall of one pH unit marks a dramatic shift towards the weak and moderate binding classes. The approach is largely unvalidated but does provide a useful framework for incorporating our mechanistic understanding of processes into wide area soil quality assessments and in identifying future research opportunities.

Notes: Abstract. Kriging is used to provide detailed quantitative information for a range of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid of data points produces spurious patterns unless the area is first partitioned into soil-geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey method with spatial statistics, the large short-range variability of acid sulphate soils means that single factor maps conceal a large element of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.

Notes: Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.

Notes: Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H2O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.The mean concentrations of H2O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Alox) and Fe (Feox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (Pox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in Pox could be explained by the routinely determined H2O-Por DL-P. Geostatistical analyses indicated that the spatial variability of Pox depended on manurial history of fields and Alox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.

Notes: Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi-sensitive and semi-tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.

Notes: A standardized dataset of derived soil properties for the 106 soil units considered on FAO-UNESCO's 1:5 million scale Soil Map of the World is presented. It was derived from a statistical analysis of the 4353 soil profiles held in the WISE (World Inventory of Soil Emission) database, which was developed at the International Soil Reference and Information Centre (ISRIC) for the geographic quantification of soil factors that control processes of global change. Median values are presented by soil unit for selected soil properties including: pH(H2O); organic carbon content; cation exchange capacity; sum of exchangeable Ca2+, Mg2+ and K+; exchangeable sodium percentage; bulk density; total porosity; available water capacity; soil drainage class; and gravel content class. Medians for these variables are presented both for the topsoil (0–30 cm) and subsoil (30–100 cm), where applicable. The data set can help to refine ratings for soil quality in global environmental models pending the availability of comprehensive georeferenced databases on soil and terrain resources such as SOTER, the World Soil and Terrain Database. In a Geographical Information System (GIS) it can be linked to the units shown on the digital Soil Map of the World through the legend code.

Notes: Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing ‘slope-specific’ grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.

Notes: Widely used summary measures of inequality or the idea of the “disappearing middle class” are potentially misleading. Divergences between evidence cited and conclusions drawn include failing to distinguish between the concepts of inequality and polarization, and using scalar “inequality” measures which are not consistent with rankings based on Lorenz curves. In addition, inappropriate claims about trends in inequality can arise from focusing on only a sub-population such as full-time male workers, and failing to account for sampling variability. These divergences are illustrated using Canadian data on labour incomes over the 1967 to 1994 period.

Notes: There are few sources of high-quality data on the dynamics of wealth accumulation. This paper uses newly available data from the 1983 89 panel of the Survey of Consumer Finances to examine household saving and portfolio change over the 1980s. Our main findings are as follows. First, median household wealth rose modestly over the period. Second, while overall wealth inequality increased, households in the top 1 percent of the wealth distribution in 1983 saw their share of total wealth decline, probably reflecting turnover among the very wealthy. Third, although age, income, and initial wealth had significant effects in regressions on household saving, a large part of the variation in saving was unexplained. Finally, there were clear life-cycle patterns in the portfolios of assets and liabilities held by households, with younger households acquiring homes, businesses and all types of debts, and older households divesting themselves of these assets and debts.

Notes: There is a growing awareness that it is important to understand patterns of family assistance; however, there is still a great deal of information about private transfers that is not known. This study begins to fill this void by presenting results from a new survey and integrating these findings with evidence from recent studies that use other new data sets. It is found that: (i) a large share of households participate in private transfer networks, (ii) a greater amount of financial assistance is provided to lower income family members, (iii) altruism does not fully explain transfer behavior, and (iv) people in their 20s and 30s receive more assistance than people of other ages, even the very old.

Notes: In this paper we analyze the determinants of material inputs into individual production activities as a function of their outputs. We use observations on a large cross-section of U.S. manufacturing plants from the Census of Manufactures, including those that make goods primary to other industries, to study differences in production techniques. We find that in most cases material requirements do not depend on whether goods are made as primary products or as secondary products. We thus elucidate support for the commodity technology model as a useful working hypothesis.

Notes: The 1993 SNA recommends chain volume indices over traditional fixed base indices as the principal measure of year-to-year volume movements in economic aggregates. Recognising, however, that “additive consistency” is important to many users, the SNA recommends that countries continue to compile traditional constant price data alongside the chain indices. In addition, the new international guidelines suggest a supply-use table framework for deriving indices. This paper considers how these demands can be met in practice. Particular attention is paid to deriving chain indices for industry value added within the same framework as that used for final demand components.

Notes: A large part of official economic data sets is produced with the help of assumed functional relations between variables. Constructing economic models on the basis of such model-generated data results in a “modeling on the basis of the results of modeling.” This common procedure can lead to consequences that seriously endanger the quality of empirical analyses. After discussing some of these dangerous consequences the authors explore the reasons behind this development. To avoid some of the most severe difficulties a “Charter for Compilation and Correct Handling of Economic Data” is proposed.

Notes: The paper shows that the Canadian System of National Accounts includes exhaustible resources but treats them as if they were produced goods. Thus, the claim that conventional accounts ignore the contribution of exhaustible natural resources is partly true. To fully account for exhaustible resources, we present an alternative national accounting framework that incorporates natural resource flows and stocks. The framework modifies the measure of the net domestic product by a factor that differs from the Hartwick-Solow-Weitzman rule and leads to different estimates of GDP, national wealth, and productivity growth. An application to the Canadian oil and gas industry shows order-of-magnitude effects.

Notes: This paper presents up-to-date estimates of the ability of non-resident fathers to pay child support. While no nationally representative data exist on the incomes of fathers, this issue has become more pertinent in recent years, as child support has become an important national issue. We find that fathers on average are able to pay nearly five times more in child support than they currently pay, and also that low income fathers can afford to pay substantially more than they actually pay. We also find that changes in nonmarital childbearing and the returns to education have had only minimal effects on trends in fathers' incomes.

Notes: In the United Kingdom there is a wide range of sources which make it possible to construct a series for components of personal wealth for the period 1920–56. The data are consistent with contemporary estimates produced for specific years in the 1920s and 1930s. They indicate that a stock-market boom and the effects of deflation and low interest rates on the nominal value of the national debt took the wealth/income ratio in the mid-1930s to a level not seen again until the housing boom of the 1980s.

Notes: The increased availability of cohort data and use of dynamic microsimulation models means that more attention is now being paid to longer term income concepts. Results are usually reported for only one income concept and a limited number of summary measures, and it is not clear whether results are influenced by the income concept used. This paper uses simulation methods to compare different approaches. For this purpose a very simple lifecycle earnings model was used to generate profiles of pre-tax incomes. Many comparisons were made using a flexible tax structure and four alternative income concepts. It was found that there was a substantial amount of agreement among the alternative concepts in making pairwise comparisons, with tentative support for the use of present values.

Notes: Using microdata from Household Budget Surveys of the Member States of the European Community, this paper examines the sensitivity of poverty statistics with respect to the choice of the equivalence scale. The results show that the ranking of the countries with respect to the overall poverty incidence is hardly affected when different equivalence scales are used. However, the composition of the poor population shows considerable changes when e.g. subjective equivalence scales are used instead of the OECD equivalence scale. The poverty incidence among specific household groups, such as single elderly and households with children, is particularly sensitive to the choice of the equivalence scale.

Notes: This paper discusses to what extent the economic growth in China in the 1980's has improved the economic well-being in urban regions of the provinces Sichuan and Liaoning and whether or not the economic growth has been attained at the cost of increased inequality. The study is based on individual household data from the State Statistical Bureau's Urban Household Survey during the 1986–90 period.

Notes: New GNP estimates in current and constant prices for the Belgian economy in the interwar period are presented. The series are conceptually and methodologically consistent with the post-World War Ii data and cover both the income and expenditure approaches. The new estimates differ considerably from the data that have been published before, casting new light on our present understanding of Belgian economic growth in the 1920s and 1930s.

Notes: While much of the evidence suggests that there was an increase in inequality in the U.S. during the 1980s, the reasons are less evident. Using the U.S. Consumer Expenditure Survey data, we find that the inequality of consumption-expenditures, as well as the inequality of other measures of resources, widened considerably during the 1980s. While previous studies suggest that increasing inequality is mainly due to increases in within group inequality, we show that by decomposing inequality by the interaction of family type and education almost three-fourths of the increase in inequality is accounted for by changes in inequality between groups and by shifts in the population.

Notes: This paper, using six waves of data (1984-89) from the United States Panel Study of Income Dynamics (PSID) and the German Socio-Economic Panel (GSOEP), compares economic well-being using single year income, multi-year income, and wealth as measures. We find inequality to be greater in the United States than in Germany regardless of the measure used. However, the relative degree of inequality varies across measures. When we disaggregate our data by age and gender categories, in general we find greater inequality in the United States, but wealth inequality among older Germans is greater than it is among older Americans.

Notes: National accounting concepts of value and income differ from their economic theoretic counterparts in two respects. Firstly, they are more precise in order to give concrete guidelines for measurement, e.g. with respect to the concept of capital formation and the treatment of taxes. Secondly, they are fundamentally different. Valuation in the national accounts is not forward-looking and not based on a notion of perfect competition. Similarly, concepts of income in the national accounts are not measures of net return to wealth or welfare and they do not intend to show income as a reward for some specific factors of production. The national accounts concepts of value and income are descriptive concepts that can only be well understood in view of the specific accounting framework to which they belong.

Notes: Can Eastern European families most severely impoverished during the transition to capitalism rely on private family safety nets? This question is likely critical for the transition's success, but little is known about family networks in Eastern Europe. We analyze newly available Polish household surveys, conducted both before and after Poland's economic transition, which measure private inter-household transfers. Such transfers are large and widespread in Poland, and in many ways appear to function like means-tested public transfers. They flow from high to low-income households and are targeted to young couples, families with many children and those experiencing illness. Private transfer patterns also suggest that they are responsive to liquidity constraints. Our results from 1987 data indicate that private transfers could fill a non-trivial portion of the income gap left by unemployment. However, we also find evidence from 1992 data suggesting that family networks weakened somewhat after the transition.

Notes: Using a nationwide household income survey, different types of income in the People's Republic of China at the end of the 1980s is analysed. The results show that various income types play quite different roles in rural and urban areas. Subsistence income makes up about half of the total income in rural China. Money income makes up about two-thirds of total income in urban China and is the major contributor to inequality in the entire country. In kind income, of which highly subsidized housing is the single most important category, is highly concentrated in urban areas and contributes greatly to inequality.