a two person dynamic equilibrium under ambiguity this paper describes a pure exchange continuous time economy with two heterogeneous agents and complete markets a novel feature of the economy is that agents perceive some security returns as ambiguous in the sense often attributed to frank knight the equilibrium is described completely in closed form after identifying agents as countries the model is applied to address the consumption home bias and equity home bias puzzles 2002 elsevier science b v all rights reserved jel classi cation d81 g11 g12 g15

optimal growth with many consumers abstract a method is described for constructing all pareto optimal allocations for a dynamic economy with many heterogeneous consumers under certainty in which both the technology and consumer preferences are recursive but preferences need not be additively separable over time optimal perfect foresight competitive equilibrium allocations are obtained through the study of a dynamic program for an economy with one consumption good sufficient conditions are given for the existence of a unique interior stationary distribution of consumption and wealth for a two person exchange economy sufficient conditions are given for the global asymptotic stability of the unique interior stationary point

a structural view of policy issues in african agricultural development comment in their paper on african agricultural development delgado and mellor henceforth dm identify two alternative paradigms the price incentive paradigm and the structural change paradigm which have been used to explain the dismal performance of the agricultural sector in sub sahara africa and to recommend policy measures designed to improve agricultural performance they argue that structural changes especially in research infrastructure and input delivery systems are the essential ingredients of a successful reform of the agricultural sector even though they do not disagree that agricultural prices should be at about the international level they claim that improved price incentives alone will not bring about the desired improvements because agriculture s aggregate supply is deemed to be highly inelastic the same view has been expressed by others e g de janvry dm state that it is widely agreed that labor is the key limiting resource to african agricultural

the impact of transport and transaction cost reductions on food markets in developing countries evidence for tempered expectations for burkina faso reductions in transport and transaction costs are expected to have a major effect on the functioning of food markets in developing countries for burkina faso this is a relevant issue as it may have important consequences for the food markets in urban and rural deficit areas a partial equilibrium model is presented to analyze the short term effects of reduced costs on price formation inter regional cereal trade and farmers and traders storage strategies our results show that the high expectations with regard to the direct effects of cost reductions on food prices and food availability require some nuance the effects of a reduction of transport costs will be small moreover also the unintended negative consequences on the competitive position of farmers and traders in other regions that do not profit from road construction should be taken into account finally it is concluded that only if transport and transaction costs are reduced simultaneously will both the consumers and farmers benefit significantly c 2004 elsevier b v all rights reserved

accelerating agricultural growth in sub saharan africa discussion the three papers presented on this theme pose and address similar central question from different perspectives thus while identifying similar problems they offer solutions which are derived from sharply contrasting views my comments as a discussant are therefore aimed toward producing something of a synthesis of the basic ideas and then offering a critique of the major postulates the papers convincingly demonstrate the magnitude of the crisis of agriculture in subsaharan africa but this unity of purpose falters when one examines the reasons given by the different papers for the rather dismal performance of the region s agricultural sector over the last two decades or so the delgado mellor paper for instance rests its case on production constraints emanating primarily from rural labor shortage according to this paper massive rural to urban labor migration over this period is at the heart of the problem rural urban migration has in turn been caused by low labor productivity in agriculture and high returns to urban employment sustained partly by increased capital inflows in comparison the matlon spencer paper sees land shortage as the primary obstacle in the way of improved performance of the agricultural sector the problem here is that according to this paper large proportions of land in sub saharan africa are not economically suitable for agricultural production either for environmental reasons or because the soils are unstable and highly variable in quality in addition and again in sharp contrast to the position taken by the delgadomellor paper rapid growth of the rural population has created tremendous pressures on agricultural land a combination of these factors has produced the land shortage constraint on agricultural expansion given the traditional farming systems and methods of sub saharan africa the delgado mellor paper suggests that more favorable price incentive policies would either not work at all or at best have very small once and for all positive impact because of the combined effects of low agricultural supply response to price changes and an inelastic labor supply curve a similar conclusion is implied in the matlon spencer paper although the culprit in this case in an inelastic supply of land

rural infrastructure transactions costs and market participation in kenya abstract we develop a conceptual framework for quantifying fixed transactions costs facing semisubsistence households using household survey data from a sample of 324 kenyan maize farmers we jointly estimate household supply and demand schedules and transactions costs econometric results indicate that on average the ad valorem tax equivalent of fixed transactions costs for households in our sample is 15 additional analysis indicates that economic isolation is positively associated with the size of transactions costs to the best of our knowledge ours are the first empirical estimates of the magnitude of fixed transactions costs for agricultural households in developing countries

computing multi period information constrained optima this paper presents a detailed theoretical derivation and justification for methods used to compute solutions to a multi period including infinite period continuum agent unobservedeffort economy actual solutions are displayed illustrating cross sectional variability in consumption and labour effort in the population at a point in time and variability for a typical individual over time the optimal tradeoff between insurance and incentives is explored and the issue of excess variability is addressed by consideration of the analogue full information economy and various restricted contracting regimes

aggregate agricultural supply response in developing countries a survey of selected issues the authors review several studies of the aggregate agricultural supply response using both economic and econometric reasons they argue that time series estimation typically generates a downward biased estimate of the response to a credible reform even though time series estimates can provide an accurate picture of past behavoiral relations they do not provide an adequate basis for forecasting the impact of policy reform this is especially true in developing countries where policy reforms involve large changes and have included agricultural price reform industrial trade liberalization financial sector reform and macroeconomic stabilization under those circumstances parameters values obtained under the former policy regime have little relevance in the new regime the authors also argue that investment in public goods should be viewed as complementary to not competitive with price policy they claim that to select the policy with the biggest impact on output makes no sense they provide what they consider to be better criteria for choosing the best from alternative policies

costs and benefits of livestock systems and the role of market and nonmarket relationships in developing countries livestock are kept not only for their physical products but also for insurance financing and to display status though this range of purposes is acknowledged livestock policies nevertheless often emphasize physical production a limited perspective that hampers the formulation and implementation of effective livestock policies this article presents a comprehensive appraisal of costs and benefits of livestock systems that takes into account the institutional environment of livestock keepers indicators are developed that capture quantify and organize not only the benefits resulting from the physical production but also those from the intangible functions the method is illustrated by an analysis of cattle in the western province of zambia the results indicate that the perspective on livestock systems developed more closely reflects the observed decisions of the livestock keepers

structure of pareto optima when agents have stochastic recursive preferences abstract a recursive method is given for constructing all pareto optimal allocations for a dynamic economy under markov certainty in which consumer preferences are recursive journal of economic literature classification numbers c60 d50

unpacking the meaning of market access evidence from rural kenya summary this paper critically examines the dimensions of market access using farm panel survey data from kenya we investigate changes in ten indicators of market access during the 1997 2010 post liberalization period we find major improvements in certain market access conditions and little change in others there is generally low correlation between alternative indicators of market access all purpose indicators may not accurately reflect specific market access conditions of interest distances to physical infrastructure are often not representative of farmers access to markets changes in specific market access conditions may have more to do with the behaviors of marketing agents we consider the implications of these findings for agricultural marketing policies and for research methods

agroindustrialization through institutional innovation transaction costs cooperatives and milk market development in the east african highlands abstract some small holders are able to generate reliable and substantial income flows through small scale dairy production for the local market for others a set of unique transaction costs hinders participation cooperative selling institutions are potential catalysts for mitigating these costs stimulating entry into the market and promoting growth in rural communities trends in cooperative organization in east african dairy are evaluated empirical work focuses on alternative techniques for effecting participation among a representative sample of peri urban milk producers in the ethiopian highlands the variables considered are a modern production practice cross bred cow use a traditional production practice indigenous cow use three intellectual capital forming variables experience education and extension and the provision of infrastructure as measured by time to transport milk to market a tobit analysis of marketable surplus generates precise estimates of non participants distances to market and their reservation levels of the covariates measures of the inputs necessary to sustain and enhance the market policy implications focus on the availability of cross bred stock and the level of market infrastructure both of which have marked effects on participation the velocity of transactions in the local community and inevitably the social returns to agroindustrialization

robust control of forward looking models abstract this paper shows how to formulate and compute robust ramsey aka stackelberg plans for linear models with forward looking private agents the leader and the followers share a common approximating model and both have preferences for robust decision rules because both doubt the model since their preferences differ the leader s and followers decision rules are fragile to different misspecifications of the approximating model we define a stackelberg equilibrium with robust decision makers in which the leader and follower have different worst case models despite sharing a common approximating model to compute a stackelberg equilibrium we formulate a bellman equation that is associated with an artificial single agent robust control problem the artificial bellman equation contains a description of implementability constraints that include euler equations that describe the worst case analysis of the followers as an example the paper analyzes a model of a monopoly facing a competitive fringe

resource degradation low agricultural productivity and poverty in sub saharan africa pathways out of the spiral sub saharan africa ssa has the lowest agricultural productivity in the world while almost half of the population lives below us 1 per day the biggest development policy challenge is to find appropriate solutions to end hunger and poverty in the region building on several years of empirical research conducted in east africa this paper identifies potential strategies for sustainable development in this region in general the empirical evidence reviewed confirms that different strategies are needed in different development domains of ssa nevertheless some elements will be common to all successful strategies including assurance of peace and security a stable macroeconomic environment provision of incentives through markets where markets function development of market institutions where they do not and public and private investment in an appropriate mix of physical human natural and social capital the differences in strategies across these domains mainly reflect differences in the mix of those investments as influenced by different comparative advantages

the global stability of efficient intertemporal allocations this paper describes a continuous time model of an economy with finitely many infinitely lived consumers and a finite number of capital goods two objectives are achieved first recursive nonadditive utility functionals are formulated and analyzed second these preference functionals are applied to analyze the nature of efficient allocations in a dynamic economy two classes of global turnpike propositions are proven which provide the basis for a model of the long run distribution of wealth these propositions also provide new perspective regarding existing stability literature based on additive utilities copyright 1987 by the econometric society

risk sharing between and within families this paper uses the panel study of income dynamics to test whether risk sharing is complete between or within american families the tests accommodate a wide variety in the configuration and availability of family data the test results reject inter as well as intra family full risk sharing even assuming that leisure is endogenous or that leisure and consumption are nonseparable

peasant household behaviour with missing markets some paradoxes explained a model of peasant household behavior under varying degrees of household specific food and labor market failures is constructed to show that these structural features can explain several well known patterns of peasant response which have often been attributed to peculiar motives presumed specific to peasants the model explains sluggish response to cash crops prices and high instability in perceived food and labor scarcities the key role of manufactured consumer goods prices in stimulating peasants effort in cash crops production the effectiveness of taxation as opposed to incentives in stimulating cash crops production and the key role of technological change in food production to enhance cash crop production results are obtained analytically in the case of one market failure and by numerical simulation with more than one

efficiency and equality in a simple model of efficient unemployment insurance abstract this paper describes the efficient allocation of consumption and work effort in an economy in which workers face idiosyncratic employment risk and considerations of moral hazard prevent full insurance we impose a lower bound on the expected discounted utility that can be assigned to any agent from any date onward and show with this feature added that the efficient unemployment insurance scheme induces an invariant cross sectional distribution of individual entitlements to utility the paper thus provides a simple prototype model suited to the study of the normative question what is the trade off between equality and efficiency in resource allocation journal of economic literature classification numbers d31 d63 d82 j65

transactions costs and agricultural household supply response we develop and estimate a model of supply response when transactions costs create a situation where some producers buy others sell and others do not participate in markets we present two rationales for why producing households may have different relationships to the market proportional and fixed transactions costs using data on mexican corn producers we estimate an empirical model that allows for separate tests of the significance of both types of transactions costs revealing that both fixed and proportional transactions costs matter for the estimation the results provide consistent estimates of supply elasticity and measures of the relative importance of factors determining both proportional and fixed transactions costs

measuring the importance of transaction costs in cattle marketing transaction cost economics recognizes that transactions do not occur in a frictionless economic environment information negotiation and monitoring costs arise in any transaction and can influence the vertical coordination outcome this paper demonstrates a method for measuring the influence of transaction costs on slaughter cattle marketing the paper focuses on the factors affecting the choice between liveweight live ring auction and deadweight direct to packer sales using tobit limited dependent variable analysis data from a survey of uk farmers are used to estimate the relative importance of various transaction costs and farm characteristic variables for the choice of marketing channel

transport costs and smallholder cropping choices an application to siaya district kenya smallholders regularly devote shares of resources to low yielding food crops than they do to cash crops that have higher market returns in this paper costly exchange is incorporated into an agricultural household model and a numerical nonseparable version of the model is used to show that seemingly inefficient cropping choices of this type in siaya district kenya can be explained as rational food import substitution given high transport costs in product markets improved rural road networks that reduce these costs could abate motives to meet food needs through domestic production and promote specialization that raises farm incomes

modeling farm households price responses in the presence of transaction costs and heterogeneity in labor markets we develop a farm household model to analyze price responses of farm households this model incorporates various types of transaction costs as well as labor heterogeneity nonproportional variable transaction costs or labor heterogeneity imply that production and consumption decisions become nonseparable even when the household buys or sells labor an empirical model is estimated using data from midwest poland the results show that nonproportional variable transaction costs and labor heterogeneity significantly influence household behavior not all price elasticities however change significantly if these are neglected

policies for sustainable development in the hillside areas of honduras a quantitative livelihoods approach in this article we use data for 376 households 1 066 parcels and 2 143 plots located in 95 villages in the hillside areas in honduras to generate information needed by decision makers to assess the needs and opportunities for public investments and design policies that stimulate natural resource conservation we develop a quantitative livelihood approach using factor and cluster analysis to group households based on the use of their main assets this resulted in seven household categories that pursue similar livelihood strategies we use a multinomial logit model to show that livelihood strategies are determined by comparative advantages as reflected by a combination of biophysical and socioeconomic variables while 92 of the rural hillsides population in honduras lives on us 1 00 capita day or less households that follow a livelihood strategy based on basic grain farming are the poorest because they often live in isolated areas with relatively poor agro ecological and socioeconomic conditions opportunities for off farm work tend to be limited in these areas and household strategies that combine on farm work with off farm work earn higher incomes per capita incomes can be increased by improving road infrastructure widening access to land policies that reduce household size and dependency ratios and adoption of sustainable land management technologies that restore soil fertility we used probit models to show that the latter can be promoted by agricultural extension programs and land redistribution investments in physical assets should be directed toward households that pursue livelihood strategies based on off farm employment or coffee production while agricultural training programs are best focused on livestock producers

a simple test of consumption insurance are consumers effectively insured against idiosyncratic shocks to income or wealth either by formal institutions such as charities private insurance and government programs or by informal mechanisms such as gifts and loans from relatives friends and neighbors under full insurance consumption growth should be cross sectionally independent of idiosyncratic variables that are exogenous to consumers this proposition is tested by cross sectional regressions of consumption growth on a variety of exogenous variables full insurance is rejected for long illness and involuntary job loss but not for spells of unemployment loss of work due to strike and an involuntary move

the dynamics of risk sensitive allocations abstract this paper describes pareto optimal allocations when agents have risk sensitive preferences as formulated by hansen and sargent ieee trans automat control 40 5 1995 968 971 necessary and sufficient conditions are given for the existence and stability of steady states at which pareto weights are time invariant when all agents are risk sensitive with the same power reward function there is a unique interior steady state which is stable when the power is positive and unstable when the power is negative when there is at least one agent with time additive preferences eventually all risk sensitive agents have zero pareto weights

the dynamics of efficient intertemporal allocations with many agents recursive preferences and production abstract the local dynamics of efficient allocations are studied for heterogeneous agent economies with production where preferences are recursive but not time separable in the case of a one sector neoclassical technology it is shown that optimal trajectories locally converge to a unique steady state provided that every agent s utility satisfies normality and increasing marginal impatience conditions in the two sector case with the above restrictions on preferences it is shown that oscillations can result only if the consumption goods sector is sufficiently capital intensive

robust permanent income and pricing i suppose there exists an extremely powerful and if i may so speak malignant being whose whole endeavours are directed toward deceiving me rene descartes meditations ii 1

raising offtake from cattle grazed on natural rangelands in sub saharan africa a transaction cost economics approach farmers in sub saharan africa are constrained by large transaction costs associated with marketing of their livestock however transaction costs are often not taken into account in the analysis of factors hampering the development of livestock marketing in this region this article empirically measures the influence of transaction costs on the offtake from cattle grazed on natural rangelands in uganda the study is based on the monitoring of 696 cattle transactions in three districts of uganda from august 2004 to august 2005 the estimated models suggest that proportional transaction costs represented by the state of roads distance to markets and time taken to reach the market are important variables constraining market participation in order to raise offtake from the national herd it is essential to explicitly address these costs one potential solution is collective action in marketing of livestock in which proportional and fixed transaction costs are reduced and shared among the group members

a selectivity model of household food marketing behavior in sub saharan africa the agricultural household s discrete decision of whether to participate in coarse grain markets is separated here from the continuous decision of how much to sell or buy conditional on participation failure to participate in markets results from high fixed transactions costs a selectivity model endogenously switches households into alternative market participation states correcting for bias caused by the exclusion of unobservable variables affecting both discrete and continuous decisions improved market information increases the probability of participation by sellers while access to cereals processing technology increases quantities transacted by both sellers and buyers conditional on participation

productivity growth and convergence in crop ruminant and non ruminant production measurement and forecasts there is considerable interest in projections of future productivity growth in agriculture whether one is interested in the outlook for global commodity markets future patterns of international trade or the interactions between land use deforestation and ecological diversity the rate of productivity growth in agriculture is an essential input yet solid projections for this variable have proven elusive particularly on a global basis this is due in no small part to the difficulty in measuring historical productivity growth the purpose of this paper is to report the latest time series evidence on total factor productivity growth for crops ruminants and non ruminant livestock on a global basis we then follow with tests for convergence amongst regions providing forecasts for farm productivity growth to the year 2040 the results suggest that most regions in the sample are likely to experience larger productivity gains in livestock than in crops within livestock the non ruminant sector is expected to continue to be more dynamic than the ruminant sector given the rapid rates of productivity growth observed recently non ruminant and crop productivity in developing countries may be converging to the productivity levels of developed countries for ruminants the results show that productivity levels may be diverging between developed and developing countries