nonconvexities in optimal pollution accumulation abstract with a few exceptions the analysis of optimal pollution accumulation or detrimental stock externalities rests on the assumptions that the level of damage is unbounded and that pollution decay increases monotonically with the level of pollution stock we show that these assumptions are restrictive and that their generalization alters the basic economic properties of optimal pollution control we specify a decay function which is concave with low stock levels and convex when pollution is higher we show that although multiple steady states may exist the globally optimal solution may be independent of the initial pollution level it is also possible that there are cutoff levels which determine the optimal long run equilibrium implying that the feedback control law is discontinuous and nonmonotonic bounded damage may have similar implications but in contrast to concave convex decay they may occur even with zero discounting

tariff preferences wto negotiations and the ldcs the case of the everything but arms initiative by assessing the impact of the recently adopted everything but arms eba initiative of the eu on the least developed countries ldcs and by showing how further multilateral trade liberalisations erode the eba preferences and impact the ldcs this paper attempts to uncover the ldcs difficult positions in the wto trade negotiations due to its limited product coverage and previous preferences granted by the eu welfare impacts of the eba on the ldcs are shown to be small and the bulk of these gains are associated with the sensitive products that are subject to gradual liberalisations moreover these small gains are likely to disappear if the eu conducts trade policy reforms in fulfilling its wto obligations resulting in an actually worse off situation for the ldcs extending the analysis to a multilateral trade liberalisation scenario reinforces the above results that the ldcs may well lose due to preference erosion and higher world market prices it concludes that other development assistance measures from developed countries should be made available to the ldcs to ease their dependency on trade preferences and to foster their supply capacities the ldcs themselves should attempt to integrate the duty and quota free market access status contained in the eba into a binding wto agreement to secure a stable trading environment but more importantly in order to solve the difficulties at the root these countries should actively engage in reforming their own trade policies

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 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

global equilibrium dynamics with stationary recursive preferences abstract we study the global dynamics of capital accumulation for a general two sector model which is not necessarily convex and where preferences of an infinitely lived agent are stationary but not additively separable we obtain monotonicity and convergence results for capital under normality assumptions on preferences and factor intensity assumptions on technology we then derive results on oscillatory dynamics under alternative factor intensity conditions or under the assumption of inferiority of future utilities finally in an exchange model with two agents we show that utilities will be monotonic or oscillatory depending on the normality or inferiority of the preferences

an empirical examination of quality certification in a lemons market i introduction researchers have long understood that a variety of mechanisms may be used to overcome problems of adverse selection stigler 1961 224 notes that s ome forms of economic organization may be explicable chiefly as devices for eliminating uncertainties in quality and akerlof 1970 cites independent groups such as the consumers union and united laboratories that test and certify the quality of goods there is however little empirical evidence that illustrates the effectiveness of such mechanisms in this article we examine the effect certification has on a market characterized by adverse selection using data from the market for young thoroughbreds we compare the performance of sales where auction houses provide certification services with sales where certification is absent the thoroughbred racehorse market consists of two distinct types of public auctions certified and noncertified sales in a certified sale auction houses physically inspect the horses nominated to their sales selling only the horses they conclude are from the upper end of the quality distribution in noncertified sales auction houses sell all horses nominated to a sale our empirical strategy is to perform tests that indicate whether adverse selection affects market outcomes in either certified or noncertified sales a finding that adverse selection is present in noncertified sales but absent in certified sales is consistent with the hypothesis that certification alleviates problems of adverse selection we adopt three approaches to test for the presence of adverse selection 1 the first approach is in the spirit of chiappori and salanie 2000 who examine the relationship between unobservable factors from participation and performance equations we model adverse selection as a case of sample selection bias and examine the correlation between errors in participation and price equations 2 to accomplish this we use a unique data set that allows us to estimate how breeder decisions to sell or retain horses affect market prices the data set consists of a 10 random sample of all thoroughbreds born in 1993 and includes both horses retained by their breeders who own a horse at the time of its birth and horses that breeders chose to sell our second test follows genesove 1993 and chezum and wimmer 1997 by examining the relationship between seller characteristics and price theoretically when observable seller characteristics are correlated with seller incentives to select goods adversely prices should reflect these differences chezum and wimmer observe that some breeders sell all of their horses whereas others retain a portion to race they find that market prices are inversely related to the extent of a breeder s involvement in racing concluding that adverse selection affects market outcomes we extend this work in two respects first we isolate the effect seller characteristics have on price through the decision to sell or retain a horse second we compare the effect seller characteristics have on observed prices in certified and noncertified sales our last test follows bond 1982 who attempts to identify adverse selection in the market for used trucks by comparing the repair records of trucks that were sold with the records of trucks retained by their original owners because the horses in our sample had not begun their racing careers at the time they were sold we use data on racetrack earnings as an ex post measure of quality and compare the quality of horses sold in noncertified sales with certified horses and horses retained by their breeders the results from each approach are consistent with certification alleviating problems of adverse selection we find that holding observable attributes constant horses that would receive unusually high market prices in noncertified sales are even more valuable in other options and are less likely to be sold in a noncertified sale

on the european responsibility in the agricultural multilateral trade negotiations modelling the impacts of the common agricultural policy the present round of multilateral trade negotiations is still deadlocked over agricultural trade the european union eu is urged by its trading partners to open its agricultural markets economic evaluations of trade liberalisation scenarios unanimously conclude that a substantial opening of agricultural markets is required for a successful welfare improving doha round in this paper we perform new evaluations to identify precisely the contributions of the european farm policy and to examine the robustness of these evaluations in the representation of this complex policy using the same specifications as in major previous studies our first simulations show that the eu has a major responsibility in delivering significant gains to the developing countries on the other hand when we conduct the same experiments with a more relevant calibration and modelling of the european farm policy instruments the gains that these developing countries may reap from the eu liberalisation are considerably reduced accordingly the current charge against the eu is simply inopportune

are trade preferences more effective than aid in supporting exports evidence from the everything but arms preference scheme this study examines the effect of the everything but arms eba trade preferences regime on exports from african caribbean and pacific countries acp to the european union eu with this aim an augmented gravity model is estimated for exports from the 79 acp countries to the eu 15 for the time period 1995 to 2005 using panel data techniques the model estimates are used to quantify the effect of the eba preferences on the acp ldcs export performance and to compare it with the impact of official development assistance in addition to their separate effects the combined impact of eba and aid flows is examined the main results do not confirm a positive effect of the eba regime on exports otherwise the combined effect of eba and aid on exports is positive supporting an eu development strategy that includes both sorts of assistance aid and trade preferences

increasing returns and crowding out abstract this paper explores how public debt interferes with the accumulation of physical capital when the technology displays a production externality of the arrow romer type we identify conditions under which a small positive amount of debt will prevent the economy from ever approaching the stock of capital that it would achieve if public debt were zero we also show that the interaction of debt and production externalities may produce bounded possibly cycling capital stock sequences in economies where sustained growth rates are possible with zero national debt finally welfare issues concerning the relation between static and dynamic inefficiencies are discussed

assessing the impact of unilateral trade policies eba and agoa on african beneficiaries exports using matching econometrics the existing literature studying the impact of non reciprocal preferential trade agreements nrptas assumes implicitly nrptas are non randomly assigned without showing the evidence of that using a matching methodology this paper investigates whether the african growth and opportunity act agoa and the everything but arms eba unilateral trade concessions have had an impact and in what magnitude on the exports of african beneficiary countries in the light of the evidence of the non random nature endogeneity of nrptas methodologically previous studies using the matching procedure focused on bi or multilateral trade agreements our work focuses on nrptas that depend only on donors conditions accordingly we show that for nrptas gravity covariates cannot be used for the matching procedure we propose to use political variables as determinants for obtaining non reciprocal trade preferences in order to address the endogenous nature of nrpta assignment our main results confirm that a country becomes eligible for a nrpta only when it meets certain conditions defined by their donors such as political stability and economic regulation for agoa and freedom of expression and human development for eba results also show that both agoa and eba policies have had a positive impact on african beneficiary countries exports to nrpta s providers even if the magnitude impact of eba is significantly lower than that of agoa

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

stationary optimal policies with discounting in a stochastic activity analysis model we consider optimal capital accumulation in a nonlinear activity analysis model in which production and primary resource supplies are affected by a stationary stochastic process of exogenous shocks the optimality criterion is the sum of discounted expected future social utilities under various neoclassical conditions on technology and preferences i there exists an optimal policy of investment and consumption expressible as a continuous time invariant function of the capital stocks and the history of stochastic shocks and ii there is a stationary stochastic process of capital stocks that is consistent with the optimal policy

agricultural liberalisation and the least developed countries six fallacies today agriculture remains the most distorted sector of the world economy therefore agricultural liberalization in the doha negotiations is rightly the top priority but the public policy discourse on the subject remains fogged by a number of fallacies these fallacies probably originated with the leadership of the world bank but have now been embraced by the imf oecd oxfam and the leading academic critics of globalization the paper identifies six fallacies and offers evidence and analysis to debunk them 1 agricultural border protection and subsidies are largely a developedcountry phenomenon 2 developed country agricultural subsidies and protection hurt the poorest developing countries most 3 developed country subsidies and protection hurt the poor rural households in the poorest countries 4 developed country agricultural protection and subsidies constitute the principal barrier to the development of the poorest developing countries 5 agricultural protection reflects double standard and hypocrisy on the part of the developed countries 6 what the donor countries give with one hand aid they take away with the other farm subsidies

eu economic partnership agreements and wto negotiations a quantitative assessment of trade preference granting and erosion in the banana market the paper provides a quantitative assessment of the impact on the banana market of the expansion of trade preferences the european union granted africa caribbean and pacific acp countries with the economic partnership agreements epa and of the possible erosion of these preferences as a result of different possible conclusions if any of on going wto negotiations the results of the simulations performed suggest that the impact of the epa on production and consumption of bananas in the eu will be limited while benefits for acp countries will be significant at the expense of most favoured nation mfn exporters an agreement between the eu and mfn countries to end the outstanding wto disputes on bananas and or the conclusion of the wto doha round may bring an erosion of the preferential margins currently enjoyed by acp countries of such an order of magnitude as to cancel out most of these benefits

the economics of non convex ecosystems introduction the word convexity is ubiquitous in economics but absent from economics in this paper we explain why and show what difference it makes to economic analysis if ecosystem non convexities are taken seriously a simple proof is provided of the connection between self similarity and power laws we also provide an introduction to each of the papers in the symposium and draw out the way in which they form a linked set of contributions

aspirations and inequality the premise of this paper is twofold first people s aspirations for their future wellbeing or that of their children aect their incentives to invest second the experiences of others help shape one s aspirations this paper marries a model of aspirations based choice with a simple theory of aspirations formation to study the relationship between aspirations and the distribution of income through its impact on investments aspirations aect economic mobility and the income distribution which in turn shape aspirations thus aspirations income and the distribution of income evolve jointly and in many situations in a self reinforcing way we study the consequences of this model for income distribution as well as for growth rates over dierent quantiles of the distribution we show that extreme equality is unstable moreover when the same aspirations are shared in a society polarization arises the theory we propose captures both the complacency stemming from low aspirations and the frustration resulting from aspirations that are too high as a result for commonly held aspirations growth rates have an inverted u shape along the income distribution

regional trade agreements versus global trade liberalisation implications for a small island developing state this study undertakes an empirical investigation of the macroeconomic and sectoral impacts of two forms of regional trade agreements vis a vis global trade liberalisation on a small island country using fiji as a case study in order to capture the feedback effects of such a complex set of policies we employ a dynamic computable general equilibrium model of the fijian economy to investigate i the impact of the pacific island countries trade agreement picta ii the impact of picta the pacific agreement for closer economic relations pacer and the economic partnership agreements epas iii the impact of full tariff liberalisation i e tariff removal only and iv the impact of full trade liberalisation with removal of both tariff and non tariff barriers while picta consistently provides the least benefits across a range of macroeconomic indicators including real output welfare trade volumes and employment full trade liberalisation involving the removal of tariff and non tariff barriers provides the greatest benefits compared to the other scenarios in terms of real output however the latter scenario is outperformed by picta pacer the epas and full tariff liberalisation in terms of welfare effects trade volumes and employment the policy implications hold important lessons for developing countries considering trade liberalisation

is equality stable economic inequality is of interest not only at some intrinsic level but also for its close connections to diverse variables ranging from economic indicators such as growth rates to sociopolitical outcomes such as collective action and conflict it is only natural then to study the evolution of inequality in an economic system it is fair to say that the dominant view on this topic is that inequality is the outcome of a constant battle between convergence and luck gary becker and nigel tomes 1979 current asset inequalities may echo into the future but their natural tendency is to die out owing to a convex investment technology disparities are only sustained through ongoing stochastic shocks see also david champernowne 1953 glenn loury 1981 a second approach emphasizes that initial conditions determine final outcomes owing principally to a nonconvex investment technology see e g mukul majumdar and tapan mitra 1982 abhijit banerjee and andrew newman 1993 oded galor and joseph zeira 1993 ray and peter streufert 1993 historical disparities may persist and magnify if such differences straddle some bifurcation threshold inequality is not inevitable in this view stable steady states with inequality coexist with others that involve perfect equality in this paper we examine a third view which emphasizes an intrinsic tendency of the market mechanism to create inequality in this approach economic inequality appears as an inevitable outcome even if all agents are identical to begin with and even if there is no uncertainty or technological nonconvexity this view has received attention in ray 1990 debasis bandyopadhyay 1993 lars ljungqvist 1993 scott freeman 1996 kiminori matsuyama 2001 and mookherjee and ray 2001 the basic argument is as follows suppose that an economy is populated by several dynasties each of which allocates resources to current consumption and bequests to descendants assume for the moment that the latter consists entirely of educational expenditures preparing children for their chosen professions of course the returns to such professions are endogenous they depend on the distribution of individuals across different professions now if several professional categories are necessary wages must adjust so as to force separation in choices even if all individuals are ex ante identical to be sure this broken symmetry matsuyama 2002 has no payoff implications for the generation alive today identical individuals must receive identical payoffs starting with the next generation however there must be inequality not just in wages but in payoffs there must be individuals in lowpaying professions that involve low training costs whose parents invested little and there must be others in high paying high trainingcost professions whose parents invested a lot once such inequality sets in it may well magnify richer offspring will find it easier to invest in better paying professions for their children two ingredients are used in this argument first credit markets must be missing or imperfect otherwise the necessary finances may be borrowed and wages net of costs must be equalized over all professions however the assumption that parents cannot borrow against their children s future earnings seems innocuous enough second parents cannot make financial bequests to supplement or substitute for educational expenditures such bequests could conceivably neutralize earnings inequality this motivates the question when might financial bequests compensate for earnings inequality in steady state moreover starting from perfect equality will equality be preserved thereafter or will inequality emerge and persist we discuss an extended example from an ongoing research project mookherjee department of economics boston university 270 bay state road boston ma 02215 ray department of economics new york university 269 mercer street new york ny 10003 and instituto de analisis economico csic barcelona spain we thank kiminori matsuyama who encouraged us to write this paper

equilibrium and optimality some imprints of david gale abstract the paper is a review of some of the themes to which david gale made lasting contributions it touches upon a number of the fundamental issues in the walrasian equilibrium theory existence uniqueness and stability the overlapping generations model non optimality and indeterminacy of competitive equilibria the von neumann equilibrium as a turnpike and in the theory of decentralized intertemporal allocation through competitive prices efficiency and golden rules duality and existence of optimal programs

the efficacy of state mandated minimum quality certification the case of used vehicles this paper investigates whether the quality certification required by certain state used vehicle disclosure laws has been effective metzger concluded from a theoretical investigation of non market responses to the lemons problem that such laws may or may not be effective we have been unable to find evidence that the currently mandated disclosure requirements in wisconsin known defects provision and iowa safety certification are effective in increasing the number of good quality vehicles traded in those used markets these disclosure requirements do not seem to decrease a prospective buyer s risk of purchasing a lemon

cherries lemons and the ftc minimum quality standards in the retail used automobile industry the ftc initially considered two forms of regulation in the used automobile market requiring dealers to either certify or warrant the mechanical condition of each automobile sold since the regulation would have been imposed only on dealers and not on private sellers its effectiveness was dependent on the magnitude of the induced shift of sales into the private market accordingly this paper employs a gametheoretic model to examine the theoretical conditions under which society could be expected to benefit from either regulatory alternative among other things it is concluded that a socially beneficial minimum quality standard may not exist in some situations

sustained endogenous growth with decreasing returns and heterogeneous capital abstract the possibility of sustained long run growth is typically associated with the presence of some endogenous engine of growth it may allow the economy to grow without bound despite the use of some non reproducible resources such situations can lead to dynamic models combining the features of sustainable growth and decreasing returns one sector models of this kind have recently attracted much attention in macroeconomics applications their approximate linearity for the purposes of long run analysis has been noted this paper is aimed at establishing the general fact dynamic models one or multi sector which are characterized by sustained endogenous growth with non increasing returns display the patterns of optimal growth asymptotically equivalent to those generated by models with linear technology i consider a neoclassical growth model with heterogeneous capital develop its linear counterpart and prove their asymptotic equivalence in terms of long run optimal growth rates and cross sectoral profiles of consumption real interest rates and relative prices this result also implies the non substitution theorem for the neoclassical dynamic model of sustained growth optimal input profiles relative prices and interest rates are asymptotically independent of intertemporal preferences

turnpike theorems in nonconvex nonstationary environments this paper provides a comprehensive development of turnpike theory in a stochastic aggregative model with time varying nonconvex technology a new approach to turnpike theorems is developed that exploits the monotonicity of optimal programs and utilizes a supermartingale process generated by stochastic euler equations this extends the classical turnpike theory to general nonconvex nonstationary environments copyright 1997 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

equipment prices human capital and economic growth abstract this paper presents a multisectoral model of economic growth in which endogenous technological progress is embodied in new equipment capital the difference in the intensity of use of human capital across sectors creates aggregate dynamic non convexities and hence the model may generate multiple balanced growth paths under standard parameter values our model can explain the observed correlations found for a pool of countries between investment rates in equipment capital and income growth on the one hand and between the rate of decline in equipment prices and income growth on the other the model is then used to study the effectiveness of two public policies that have been widely implemented to promote economic growth an equipment investment tax credit and a tax incentive to human capital accumulation our results indicate that both policies have positive effects on equipment investment and on long run growth

dynamic interaction models of economic equilibrium abstract the paper develops a stochastic dynamic model of economic equilibrium with locally interacting agents the main focus of the study is on the modeling of market interactions those arising in connection with commodity exchange and regulated by price mechanisms the mathematical framework is a control theory for random vector fields on directed graphs the graphs involved serve to describe the spatio temporal structure of commodity flows in the system the main results are concerned with the existence uniqueness and stability of stochastic dynamic equilibria

the efficiency of used vehicle markets the case of technological obsolescence and differential repair records this paper examines the effect of technological oboslescence differential maintanance expenditures and differential fuel efficiencies on the depreciated value of automobiles our results support the widely held belief that used vehicle markets are efficient we show that the significant decline in the depreciated values of used automobiles is predominantly due to age we also conclude that technological obsolescence causes a once and for all decrease in the depreciated value of used automobiles that for imported vehicle lines differential maintanance expenditures affect depreciated value and that for domestic vehicle lines differential fuel efficiencies impact depreciated value

uneven growth a framework for research in development economics the textbook paradigm of economy wide development rests on the premise of balanced growth that is on the presumption that all sectors will grow in unison over time as a country gets richer this view has served us reasonably well in some circumstances but is not particularly useful for accounts of modern under development in many developing countries economic growth has been fundamentally uneven software development the outsourcing of services sectoral technological change quick compositional shifts between agriculture and other sectors the rise of particular exports special economic zones and so on this paper will discuss both the sources of uneven growth and its implications with greater emphasis on the latter the paper will argue that much of the distributional issues or the reactions to globalization that we see in modern developing societies can be viewed as reactions to a growth process that is fundamentally uneven and is indeed perceived as such