renewable natural resource management and use without markets natural resources by their nature are not readily bent to the status of private property efficient resource use is complicated by jurisdictional externalities public goods non use values and beneficiaries spatially separated from the location of resources the task is made more challenging by ecological complexity that obscures cause benefits and effects costs and dramatic time lags between individual actions and subsequent social consequences that together with substantial uncertainty introduce the chance of irreversibilities resource economists have played a major role in the literature on externalities the development of individual transferable quotas non market valuation techniques and common property management

on the economically optimal exploitation of a renewable resource the case of a convex environment and a convex return function we investigate optimal policies for the exploitation of a renewable resource subject to a concave growth function and a convex return function we prove an important result on the elasticity of the objective function and apply it to give a characterization of the optimal harvesting paths in this class of models in particular we derive conditions such that all optimal programs converge to a fixed point or to a cycle of finite period and hence result in the conservation of the resource we also show which assumptions guarantee that extinction of the stock is optimal that nonconvex preferences or technologies cause problems for economic theory is well known as our model can formally be interpreted as an optimal growth model with nonconcave utility function our results are a further contribution on the dynamics of optimal paths in the general class of economic models with nonconcavities journal of economic literatureclassification numbers c61 e32 q20

a note on the extinction of renewable resources abstract this paper presents two sets of conditions under which a sole owner of a renewable resource stock who maximizes a nonlinear benefit function would find it more profitable to harvest the stock to extinction than follow a continuous harvesting strategy when the minimum viable resource stock is positive extinction is optimal as long as the initial resource stock is sufficiently small regardless of the discount rate when the minimum viable resource stock is zero and the discount rate exceeds the growth potential of the species extinction is optimal for sufficiently small initial stocks

a nonsmooth nonconvex model of optimal growth this paper analyzes the nature of economic dynamics in a one sector optimal growth model in which the technology is generally nonconvex nondifferentiable and discontinuous the model also allows for irreversible investment and unbounded growth we develop various tools to overcome the technical difficulties posed by the generality of the model we provide sufficient conditions for optimal paths to be bounded to converge to zero to be bounded away from zero and to grow unboundedly we also show that under certain conditions if the discount factor is close to 1 any optimal path from a given initial capital stock converges to a small neighborhood of the golden rule capital stock at which sustainable consumption is maximized if it is maximized at infinity then as the discount factor approaches 1 any optimal path either grows unboundedly or converges to an arbitrarily large capital stock

on conservation of renewable resources with stock dependent return and nonconcave production textabstractthis paper analyzes conservation and extinction of renewable resources when the production function is nonconcave and the return function depends on consumption and the resource stock the paper focuses on the efficiency of global conservation a safe standard of conservation and extinction which outcome obtains depends on the marginal rate of substitution between investment and the stock in addition to the discount factor and the marginal productivity of the resource conservation may be efficient even if the discounted intrinsic growth rate of the resource is less than 1 journal of economic literature classification numbers d90 q20

stochastic dynamic models with stock dependent rewards abstract we examine the behavior of optimal consumption and investment policies in aggregate stochastic growth models when utility depends on both consumption and the stock level such models arise in the study of renewable resources monetary growth and growth with public capital conditions are given which guarantee that optimal policies are monotonic the limiting behavior of the optimal consumption investment and output processes is characterized

government fertilizer subsidy and commercial sector fertilizer demand evidence from the federal market stabilization program fmsp in nigeria abstract we examine how the previous fertilizer subsidy program in nigeria fmsp affected the demand for commercial fertilizer we apply an endogenous double hurdle model to a pseudo panel and cross section data of farm households the methodology accounts for potential endogeneity of commercial fertilizer price with subsidy our specification is also appropriate where few farmers report the use of both subsidized and commercial fertilizer we find that 100 kg of subsidized fertilizer supplied to a farm household reduced the probability of its participation into commercial fertilizer market by 10 21 points while not affecting fertilizer use upon participation

agriculture in africa telling myths from facts a synthesis stylized facts drive research agendas and policy debates yet robust stylized facts are hard to come by and when available often outdated in a special issue of food policy 12 papers revisit conventional wisdom on african agriculture and its farmers livelihoods using nationally representative surveys from the living standards measurement study integrated surveys on agriculture initiative in six african countries at times the findings simply confirm the common understanding of the topic but the studies also throw up several surprises redirecting some policy debates while fine tuning others overall the project calls for more attention to checking and updating the common wisdom this requires nationally representative data and sufficient incentives among researchers and policy makers alike without well grounded stylized facts they can easily be profoundly misguided

rural nonfarm activities and agricultural crop production in nigeria although most rural households are involved in the farm sector the nonfarm sector has grown significantly in recent decades and its role in rural development has become increasingly important this article examines the effect of participation in nonfarm activities on crop expenses of farm households in nigeria the relationship is modeled using a nonseparable agricultural household model that suggests that participating in nonfarm activities can relax the credit constraints facing farm households and reduce risk thereby helping households improve farm production and smooth consumption over time the results show that participation in nonfarm activities by nigerian farmers has a positive and significant effect on crop expenses and in particular on payments for hired labor and inorganic fertilizers separate analysis of the six geopolitical zones in nigeria indicates that it is in the south south and south east zones where nonfarm participation appears to induce more hiring of labor the results support the hypothesis that nonfarm participation helps relax liquidity constraints but suggests how that liquidity is used is zone specific in general the results also indicate that liquidity is used more to pay for inputs into staple production as opposed to cash crops

adoption of agricultural innovations in developing countries a survey this paper reviews various studies which have provided a description and possible explanation to patterns of innovation adoption in the agricultural sector the survey points out that the tendency of many studies to consider innovation adoption in dichotomous terms adoption nonadoption may not be appropriate in many cases where the actual decisions are defined over a more continuous range more attention needs to be given to the socio cultural and institutional environment in area studies so that their interrelation with economic factors affecting adoption can be inferred the presence of several interrelated innovations is another aspect that needs to be considered more carefully in future research since a number of simultaneous decisions may be involved furthermore the possibility of regular sequential patterns in adopting components of a new technological package should be specifically addressed in future studies finally the impact of differential adoption rates on land holding distribution merits attention in future research

dynamic programming models of fishing competition it is natural to consider the stock of any renewable resource as a capital stock and treat the exploitation of that resource in much the same way as one would treat accumulation of a capital stock this has been done to some extent by cohn clark and gordon monro and by ngo van long whose papers contain a discussion of this point of view however the analysis is much simpler than it appears in the literature especially since the interaction between markets and the natural biological dynamics has not been made clear three issues which have been raised only tangentially are important for the understanding of the economics of renewable resources the first arises from the fact that the fish population might not be able to sustain the market determined amount of fish and hence should be allocated optimally over time second there is the cost externality here costs are affected by the size of the stock of fish which again affects the optimal allocation over time the third issue is how central planning typically used in capital theory can be employed as a tool in analyzing a decentralized economy with perfect futures markets and property rights in this paper a simple framework using only elementary mathematical techniques will be provided in which many important results new to the literature as well as many familiar results can be derived one bonus of this approach is that much of the previous literature can be organized and rationalized the simplicity of the mathematics has the effect of revealing the underlying economic intuition of the subject throughout the paper as a matter of convenience the selfrenewing resource will be referred to as fish however it should be clear that the analysis is perfectly general in that it can be applied to any self renewing resource in fact by specializing the production function an elementary exposition of the theory of exhaustible resources is implicit there are two main sections to this work plus an appendix the first section analyzes the time path of prices output and resource stock under the assumption of free entry competition and the second section studies optimal planning or perfect competition in the first part of the discussion of each market structure extraction costs are assumed to be independent of the size of the fish stock in the second part of each section this assumption is relaxed finally the appendix contains several of the results used in the body of the paper the case of free entry competition can be treated in a very simple manner each period s output is determined by the intersection of the demand and marginal harvesting cost curves i e supply equals demand subtracting this output from the natural dynamics yields the dynamics of free entry competition using this technique it is easy to see the conditions under which free entry competition leads to the exhaustion of the stock of fish furthermore the free entry case serves as a benchmark by which to evaluate the effects of the institution of property rights on the exploitation of the resource the case of a centrally planned economy is studied next this case is shown to be identical to a competitive outcome in which property rights are clearly defined and prices and outputs are endogenously determined so as to be consistent with demand conditions one result coincidentally is that it is possible that the optimal solution might be obtained without property rights the tech the hebrew university university of virginia university of illinois and northwestern university respectively research support from the national science foundation under grants soc 77 27340 and soc 7905900 and the us israel bsf under grant 1828 79 is gratefully acknowledged

a complete characterization of optimal growth paths in an aggregated model with a non concave production function the convexity of technology has played a crucial role in economic analyses of optimal one sector growth problems for example two of the key results on the traditional model of ramsey 1928 that have relied on the convexity of the technology are that optimal intertemporal growth involves moving monotonically towards a unique steady state as in cass 1965 koopmans 1965 and that the value function is a concave differentiable function of the initial capital stock as in benveniste and scheinkman 1979

farm productivity in burkina faso effects of animal traction and nonfarm income the purpose of this invited paper is to stimulate at the micro meso and macro levels debate on positive analytical approaches to agricultural productivity the session focuses on africa because it is the only developing region where crop output and yield growth is lagging seriously behind population growth the present paper treats the micro farmhousehold level macro and meso analyses are useful for tracing productivity effects of policy and infrastructure change employing broad samples over long periods micro analyses tend to track smaller samples over shorter periods but dig below the aggregate surface to discern and explain productivity differences over crops zones and farmer groups micro analysis is useful for policy and technology formulation and for infrastructure and commodity promotion strategies further many aggregate studies are limited to only a few composite product categories because of lack of more detailed data on labor land and capital allocations over crops to obtain finer distinctions among crops one needs detailed farm management surveys since the spate of african farm management studies in the 1960s and 1970s soils have rapidly degraded access to land has become increasingly constrained factor and credit markets have changed structurally and nonfarm activity by farm households has apparently increased these changes should affect productivity across farm types suggesting the need to revive attention to farm level analysis past farm level productivity work in africa which largely used positive analysis tended to stratify the sample exogenously based on farm characteristics generally by farm size use of animal traction access to credit use of new seed varieties land tenure status or income we follow these earlier studies by stratifying the farm household data by a factor we expect to affect technical parameters namely farm capital in the guinean zone of burkina faso in particular we stratify according to whether the household owns animal traction equipment foll wing barrett et al and jaeger and matlon besides adding to empirical evidence on the productivity effects of animal traction we endogenously stratify the sample with a selectivity model an approach too rarely taken with a few recent exceptions such as carter in productivity research we then estimate production functions controlling for selectivity bias such an approach also allows us to test the indirect effect of nonfarm income on productivity through its effect on technology adoption as embodied in farm capital acquisition studies of nonfarm income effects on capital acquisition are not absent in the literature e g barrett et al in eastern burkina but they have been somewhat neglected in farm level work and neglected even more in aggregate level research because of the rarity of rural nonfarm income data

the rural non farm economy prospects for growth and poverty reduction summary policy makers have high expectations for the rural non farm economy rnfe given high income shares growing employment and frequently low capital requirements they see the rnfe as a potential pathway out of poverty for their rural poor yet available evidence suggests that pro poor rural non farm growth does not occur automatically for the poor to benefit from rural non farm growth policy makers must stimulate buoyant rural economies with robust non farm income growth not simply low productivity employment moreover the poor must gain access to growing market niches fluid labor markets provide one important bridge linking the rural poor to growing non farm opportunities

one sector nonclassical optimal growth optimaility conditions and comparative dynamics the authors consider a one sector nonclassical model of optimal economic growth characterized by a convex concave production function they provide in a dynamic programming context a characterization of all local interior maximum of the miximand of the bellman equation these conditions are the euler equation and a second order condition namely that the marginal propensity to consume is less than one an example is used to illustrate these conditions also several comparative dynamic results are derived in particular it is shown that the maximum and minimum selections out of the optimal consumption correspondence shift down as the discount factor increases copyright 1991 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

nonparametric engel curves and revealed preference this paper applies revealed preference theory to the nonparametric statistical analysis of consumer demand knowledge of expansion paths is shown to improve the power of nonparametric tests of revealed preference the tightest bounds on indifference surfaces and welfare measures are derived using an algorithm for which revealed preference conditions are shown to guarantee convergence nonparametric engel curves are used to estimate expansion paths and provide a stochastic structure within which to examine the consistency of household level data and revealed preference theory an application is made to a long time series of repeated cross sections from the family expenditure survey for britain the consistency of these data with revealed preference theory is examined for periods of consistency with revealed preference tight bounds are placed on true cost of living indices

competitive equilibrium cycles recently there has been a surge of interest in endogenous business cycles that arise in competitive laissez faire economies in the context of standard overlapping generations economies conditions for the existence of equilibrium cycles have been given by grandmont 1983 and by benhabib and day 1982 models of the economy with extrinsic uncertainty or sunspots that have been developed by shell 1977 and by cass and shell 1983 see also balasko 1983 can also lead to equilibrium cycles

links between nonfarm income and farm investment in african households adding the capital market perspective farm household surveys in the 1970s and 1980s showed that nonfarm activities provide an important share of household income contrasting with the conventional image of rural african households as deriving their food entitlement almost exclusively from the land e g matlon collier and lal low reardon et al haggblade hazell and brown much of the literature on nonfarm income has concentrated

agricultural input credit in sub saharan africa telling myth from facts recent evidence shows that many sub saharan african farmers use modern inputs but there is limited information on how these inputs are financed we use recent nationally representative data from four countries to explore input financing and the role of credit therein a number of our results contradict conventional wisdom found in the literature our results consistently show that traditional credit use formal or informal is extremely low across credit type country crop and farm size categories instead farmers primarily finance modern input purchases with cash from nonfarm activities and crop sales tied output labor arrangements which have received little empirical treatment in the literature appear to be the only form of credit relatively widely used for farming

on the existence of a stationary optimal stock for a multi sector economy a primal approach abstract using a purely primal approach we show the existence of a non trivial stationary optimal stock for a multi sector economy our result generalizes earlier work by dropping the productivity assumption and by replacing the continuity hypothesis on the utility function by upper semicontinuity

rural livelihoods and poverty reduction strategies in four african countries this paper compares and contrasts rural livelihoods in uganda kenya tanzania and malawi with a view to informing rural poverty reduction policies within poverty reduction strategy plans prsps low household incomes in rural areas of all countries are associated with low land and livestock holdings high reliance on food crop agriculture and low monetisation of the rural economy these adverse factors are in some instances made more difficult by land sub division at inheritance declining civil security in rural areas deteriorating access to proper agronomic advice and inputs and predatory taxation by decentralised district councils better off households are distinguished by virtuous spirals of accumulation typically involving diverse livestock ownership engagement in non farm self employment and diversity of on farm and non farm income sources lessons for prsps centre on the creation of a facilitating rather than blocking public sector environment for the multiplication of non farm enterprises seeking creative solutions to the spread of technical advice to farmers and examining critically the necessity for and impact of tax revenue collection by district councils on rural incomes and enterprise

global value chains large scale farming and poverty long term effects in senegal this paper presents panel data evidence on the impact of expansion of global value chains and large scale export oriented farms in developing countries over almost a decade we estimate the income effects of wage employment on large scale farms in the horticultural export sector in senegal using data from two survey rounds covering a seven years period of rapid expansion of the sector we estimate average income effects as well as heterogeneous income effects using fixed effects and quantile fixed effects regressions we find that poverty and inequality reduced much faster in the research area than elsewhere in senegal employment in the horticultural export sector is associated with higher household income and the income effect is strongest for the poorest households expansion of the horticultural export sector in senegal has been particularly pro poor through creating employment that is accessible and creates substantial income gains for the poorest half of the rural population these pro poor employment effects contrast with insights in the literature on increased inequality from rural wage employment

expanding access to agricultural inputs in africa a review of recent market development experience abstract this paper asks what can be done to expand input use in africa and can it be done in a manner that supports continued growth of private sector input markets the precarious food security situation in many african countries has prompted governments and donors to use input distribution or credit programs as a means of rapidly increasing food supply for the poor these efforts however often reduce the ability of input market development programs to stimulate commercial interest in input supply a review of both types of programs describes recent efforts to address constraints to expanded input use and finds that further expansion is often constrained by inadequate investment in a variety of public goods needed to stimulate input led agricultural intensification rather than continuing to invest resources in programs to provide inputs or credit directly to farmers governments with donor assistance should consider shifting their focus to the serious deficiencies in the provision of public goods roads irrigation basic education market information systems research and extension and improved institutions contract law and enforcement systems of grades and standards improvements in these areas can both lower costs of supply and increase farm level demand creating a situation where the private sector will have greater incentives to expand input distribution networks to zones and farmers who currently do not have access

moving up or moving out insights into rural development and poverty reduction in senegal summary while worldwide progress in poverty reduction has been impressive sub saharan africa is lagging behind with slow growth and a high poverty headcount ratio there are fierce debates on how sub saharan africa can foster pro poor growth and the role of agriculture and small versus large scale farming in poverty reduction we contribute to this debate with micro economic empirical evidence from the senegal river delta an area that recently experienced rapid rural development we use household survey data from two panel rounds in 2006 and 2013 and a cluster analysis to investigate livelihood income and poverty dynamics in the region we find that with 4 3 annual growth in average household income 29 5 percentage points poverty reduction and 4 2 percentage points inequality reduction over the period 2006 13 development in the senegal river delta region has been remarkably pro poor income growth and poverty reduction have been most impressive among households moving into wage employment on large scale horticultural export farms and in an emerging service sector income growth in small scale agriculture and non farm businesses has been more modest but has affected the largest number of households transformation in both farm and non farm sectors has driven rural development in the senegal river delta region and investments in both large and small scale agriculture have contributed importantly to household income growth and poverty reduction our findings imply that foreign investments in large scale commercial and export oriented farming can trigger pro poor growth directly through employment effects and indirectly through investment and consumption linkages with the small scale farm and non farm sector

migration remittances and agricultural productivity in china in our paper we have used the new economics of labor migration framework to trace the complex linkages that exist among migration remittances and agricultural productivity in china constraints in the operation of on farm labor and capital or insurance markets or institutions provide households with a motivation to migrate and distort on farm operations when labor leaves in our household sample the net impact of migration and remittances on maize production is negative excerpt

behavioural and material determinants of production relations in agriculture in this essay we develop a framework for analysing the major institutions governing the production and exchange of output and the primary factors of production in rural areas the analysis incorporates general considerations of risk and information constraints jointly with the principal material attributes of agriculture and of agricultural production factors the framework is used to analyse barriers to the existence of the major intertemporal and factor markets it is applied specifically to land scarce environments for which it provides an internally consistent explanation for many of the well documented institutional features of such settings in addition the analysis provides new implications for among other phenomena the inter relationships among ownership holdings operational scale family size and factor productivity for the scarcity of animal rental markets and use of animals as collateral for the renting out of land by small landowners and for the existence of plantations for certain crops

rural nonfarm employment and farming household level linkages this article introduces the articles in agricultural economics vol 40 no 2 march 2009 first we introduce their objectives in a brief review of existing literature on developing country trends in rural income diversification in particular rural nonfarm employment rnfe and its impact on farm technology choice in crops and livestock and thus on agricultural modernization and diversification then we preview the key points of the articles which use distinctive primary datasets from albania bulgaria china india mexico nigeria the philippines senegal and vietnam to document the impacts of rnfe and their implications for farm technology and farm activity

the future of small farms new directions for services institutions and intermediation summary efficient pre and post harvest services are essential if small farms in high potential areas are to intensify production contribute to economic growth and reduce poverty they also matter if small farms in marginal areas are to manage their natural resource base in the face of growing population pressure and climate change difficulties that smallholders face in accessing services are reviewed showing how incentives for commercial delivery of services to smallholders differ between staple food traditional cash crop and high value product supply chains the major challenge in service delivery to smallholders in much of africa concerns coordination of service development and delivery different forms of intermediary institution for achieving such coordination are examined

does nonagricultural labor relax farmers credit constraints evidence from longitudinal data for vietnam we examine the relationship between participation in nonagricultural labor activities and farming production decisions focusing on the use of inputs using longitudinal data for vietnam from 1993 to 1998 we find that households engaged in nonagricultural labor spend significantly more on seeds services hired labor and livestock inputs this is consistent with the hypothesis that nonagricultural labor income relaxes credit constraints to farming

consumption risk technology adoption and poverty traps evidence from ethiopia much has been written on the determinants of input and technology adoption in agriculture with issues such as input availability knowledge and education risk preferences profitability and credit constraints receiving much attention this paper focuses on a factor that has been less well documented the differential ability of households to take on risky production technologies for fear of the welfare consequences if shocks result in poor harvests building on an explicit model this is explored in panel data for ethiopia historical rainfall distributions are used to identify the counterfactual consumption risk controlling for unobserved household and time varying village characteristics it emerges that not just ex ante credit constraints but also the possibly low consumption outcomes when harvests fail discourage the application of fertilizer the lack of insurance causes inefficiency in production choices