foreign aid tariffs and nontraded private or public goods abstract the possibility of transfer paradoxes or immiserizing growth in tariff ridden small open developing countries with a nontraded goods sector is analysed in four models a short run sector specific factor model a dual economy model capital is mobile between some but not all sectors a long run model factors are mobile between all sectors and a model with public goods several results of the received literature on transfer paradoxes and or immiserizing growth in distorted small open economies are generalized to nontraded private and public goods allowing for intersectoral factor mobility or immobility

monetary union in west africa and business cycles synchronicity new evidence in the light of the initiative of the west african monetary zone wamz to introduce a common currency by 2020 this paper investigates the intricacies of the business cycles synchronicity among the six countries given i the rising importance of trade and cooperation with china ii the consideration of the euro as a potential anchor currency and a vehicle for trade with the eurozone and iii the importance of nigeria as the largest country of the group and the main supplier of oil we investigate the relative importance of these three major players in having their business cycles linked with the group in addition we investigate the underlying determinants of the business cycles synchronicity among the wamz countries on a pairwise basis results show a clear dominance of china s business cycle synchronicity with the wamz over europe s and nigeria s trade integration emerges as the key underlying factor of the common cycle observed

is the cfa franc zone an optimum currency area summary in this paper we explore the features of the cfa franc zone and compare them to those of the economic and monetary union emu by operationalizing the criteria for an optimum currency area a structural vector autoregression method is used in modeling national outputs as determined by global regional and country specific shocks we find that domestic outputs of the cfa franc zone countries are strongly influenced by country specific shocks while regional shocks are far more important in european countries that have joined the emu the results suggest that the cfa franc zone countries are structurally different from each other and thus are more likely to be subjected to asymmetric shocks they do not appear to form an optimum currency area and the monetary union may have been a costly arrangement for the member countries unless they are compensated with some other benefits

modelling macroeconomic shocks in the cfa franc zone abstract in this paper we modify the method of blanchard and quah american economic review 79 1989 655 in order to estimate a structural var model appropriate for a small open economy in this way we identify shocks to output and prices in the members of the two monetary unions that make up the african cfa franc zone the costs of monetary union membership will depend on the extent to which price and output shocks are correlated across countries and the degree of similarity in the long run effects of the shocks on the macroeconomy the policy conclusions depend on the relative importance of different macroeconomic variables to policymakers and the speed with which a policymaker is able to respond to a shock

installed base and compatibility innovation product preannouncements and predation a good is often more valuable to any user the more others use compatible goods the authors show that this effect may inhibit innovation if an installed base exists and transition to a new standard must be gradual early adopters bear a disproportionate share of transient incompatibility costs this can produce excess inertia the installed base however is stranded if the new standard is adopted this may create excess momentum these dynamic effects have strategic implications temporary price cutting can permanently prevent entry and product preannouncements can be critical in innovation these strategic actions have ambiguous welfare effects

is regional integration in the cfa zone sustainable this article aims to study the long term sustainability of regional integration in the communaute financiere africaine cfa zone based on the theory of the endogeneity of monetary zones to this end we consider trade and intra cfa migration as the two quantitative vectors of regional integration using robust estimation techniques to overcome the endogeneity bias our results show that integration in the cfa zone is moderately sustainable more precisely while the monetary unions of the cfa zone in particular that of the waemu contribute to reinforcing the intra regional mobility of goods and people they fail to induce strong synchronization of the macroeconomic cycles

aggregate comparative statics abstract in aggregative games each player s payoff depends on her own actions and an aggregate of the actions of all the players many common games in industrial organization political economy public economics and macroeconomics can be cast as aggregative games this paper provides a general and tractable framework for comparative static results in aggregative games we focus on two classes of games 1 aggregative games with strategic substitutes and 2 nice aggregative games where payoff functions are continuous and concave in own strategies we provide simple sufficient conditions under which positive shocks to individual players increase their own actions and have monotone effects on the aggregate the results are illustrated with applications to public good provision contests cournot competition and technology choices in oligopoly

terms of trade and domestic distribution export led growth with abundant labour abstract a general equilibrium macro model is constructed to explore effects of export led growth policies on the terms of trade and the domestic distribution of a developing region with abundant labour this region the south trades with another the north they have different technologies and supplies of factors it is shown that under certain conditions of dualism in the production of goods and of abundant labour supply in the south an increase in the volume of exports from the south may bring about a sustained worsening of the south s terms of trade with the north even if this increase in exports is due to a positive shift in demand from the north this change in the terms of trade is accompanied by a sustained loss of purchasing power of wages within the south these results take place in a walrasian stable market when technologies are more homogenous and labour less abundant the results are reversed increased exports will take place together with improvements in terms of trade and a tendency to equalise factor prices between the regions the results argue for coordination of domestic and international policies with special attention to technologies and labour markets

adjustment and economic performance under a fixed exchange rate a comparative analysis of the cfa zone abstract this paper examines the economic performance of the cfa franc zone versus non cfa countries in recent years a modified control group approach is used to compare the evolution of macro economic indicators in the cfa countries vis a vis other sub saharan african countries controlling for initial conditions changing exogenous internal and world environment and policy stance in addition our approach allows for a formal testing of whether zone membership is a random the implication of randomness i e no selection bias is that the cfa zone economies would have performed in the same fashion as the rest of sub saharan africa for example in the absence of the zone our results show that the randomness assumption is only valid for the cases of gdp growth and inflation for other indicators savings investment and export ratios to gdp the decision to participate in the zone is endogenous and is related to the expectation of improved economic performance subsequently in the estimation of the zone s effects on the latter group of indicators we corrected for the ensuing sample selectivity bias by estimating that status indicator participation versus non participation via a probit model our estimation results indicate a weakening competitive position of the cfa members during the second half of 1980s relative to the first half compared with the non cfa countries in terms of output growth as well as the performance of exports investment and savings the exception is domestic inflation with the cfa countries faring better on that front results for a longer term comparison the 1970s versus the 1980s are somewhat mixed while the estimated coefficients for the marginal effect of zone participation corroborates a better performance for the cfa zone over the group of comparators in terms of exports domestic savings and investment and inflation the zone failed to distinguish itself with regard to economic growth in the long run

hard or soft pegs choice of exchange rate regime and trade in africa summary this paper revisits the link between fixed exchange rate regimes and trade in the context of africa s exchange rate arrangements differentiating the effects of hard pegs currency unions from conventional soft pegs using a novel dataset of exchange rate regime classification the paper augments the gravity model of bilateral trade flows with measures of currency unions and conventional pegged arrangements and benchmarks africa s experience against the rest of the world we find that in both samples currency unions and pegs increase trade vis a vis more flexible exchange rate arrangements through channels in addition to reduced exchange rate volatility however the effect is almost twice as large for africa in addition the trade generating effect of pegs is at least as large for africa as that of currency unions suggesting that pegs could present a viable option perhaps an alternative to currency unions to promote trade in the region

correlated equilibrium as an expression of bayesian rationality if it is common knowledge that the players in a game are bayesian utility maximizers who treat uncertainty about other players actions like any other uncertainty then the outcome is necessarily a correlated equilibrium random strategies appear as an expression of each player s uncertainty about what the others will do not as the result of willful randomization use is made of the common prior assumption according to which differences in probability assessments by different individuals are due to the different information that they have where information may be interpreted broadly to include experience upbringing and genetic makeup copyright 1987 by the econometric society

rationalizable strategic behavior the notion of equilibrium proposed by nash 19 has come to play a dominant role in economic applications of noncooperative games while analyses of nash equilibria have unquestionably contributed to our understanding of economic behavior it would be unreasonably optimistic to maintain that nash solved the problem of noncooperative strategic choice there is a small literature beginning with ellsberg 6 and a much larger oral tradition which argues that nash behavior is neither a necessary consequence of rationality nor a reasonable empirical proposition in this paper i take the view that although there may be various reasons why an agent might select a nash strategy the notion of an equilibrium has little intrinsic appeal within a strategic context when an agent reaches a decision in ignorance of the strategies adopted by other players rationality consists of making a choice which is justifiable by an internally consistent system of beliefs rather than one which is optimal post hoc this point of view is not original indeed most serious justifications of the nash hypothesis embrace such an approach arguing that agents will expect the game to yield a nash outcome and consequently will choose their equilibrium strategies nevertheless when we think in terms of maximizing utility subject to expectations rather than realizations it becomes clear that the nash hypothesis far from being a consequence of rationality arises from certain restrictions on agents expectations which may or may not be plausible depending upon the game being played we are then quite naturally led to ask are there any restrictions of individuals expectations and hence choices which are required by rationality alone rather than by subjective plausibility this paper is concerned with defining justifying characterizing and refining a criterion for rational strategic choice which i label rationalizability

rationalizable strategic behavior and the problem of perfection this paper explores the fundamental problem of what can be inferred about the outcome of a noncooperative game from the rationality of the players and from the information they possess the answer is summarized in a solution concept called rationalizability strategy profiles that are rationalizable are not always nash equilibria conversely the information in an extensive form game often allows certain unreasonable nash equilibria to be excluded from the set of rationalizable profiles a stronger form of rationalizability is appropriate if players are known to be not merely rational but also cautious what constitutes rational behavior in a noncooperative strategic situation this paper explores the issue in the context of a wide class of finite noncooperative games in extensive form the traditional answer relies heavily upon the idea of nash equilibrium nash 17 the position developed here however is that as a criterion for judging a profile of strategies to be reasonable choices for players in a game the nash equilibrium property is neither necessary nor sufficient some nash equilibria are intuitively unreasonable and not all reasonable strategy profiles are nash equilibria the fact that a nash equilibrium can be intuitively unattractive is well known the equilibrium may be imperfect introduced into the literature by selten 20 the idea of imperfect equilibria has prompted game theorists to search for a narrower definition of equilibrium while this research some of which will be discussed here has been extremely instructive it remains inconclusive theorists often agree about what should happen in particular games but to capture this intuition in a general solution concept has proved to be very difficult if this paper is successful it should make some progress in that direction the other side of the coin has received less scrutiny can all non nash profiles really be excluded on logical grounds i believe not the standard justifications for considering only nash profiles are circular in nature or make gratuitous assumptions about players decision criteria or beliefs the following discussion of these points is extremely brief due to space constraints more detailed arguments may be found in pearce 18

equilibrium bias of technology this paper presents three sets of results about equilibrium bias of technology first i show that when the menu of technological possibilities only allows for factor augmenting technologies the increase in the supply of a factor induces technological change relatively biased toward that factor meaning that the induced technological change increases the relative marginal product of the factor becoming more abundant moreover this induced bias can be strong enough to make the relative marginal product of a factor increasing in response to an increase in its supply thus leading to an upward sloping relative demand curve i also show that these results about relative bias do not generalize when more general menus of technological possibilities are considered second i prove that under mild assumptions the increase in the supply of a factor induces technological change that is absolutely biased toward that factor meaning that it increases its marginal product at given factor proportions the third and most important result in the paper establishes the possibility of and conditions for strong absolute equilibrium bias whereby the price marginal product of a factor increases in response to an increase in its supply i prove that under some regularity conditions there will be strong absolute equilibrium bias if and only if the aggregate production function of the economy fails to be jointly concave in factors and technology this type of failure of joint concavity is possible in economies where equilibrium factor demands and technologies result from the decisions of different agents

benefits from mutual restraint in a multilateral monetary union summary we show that monetary union can enhance price stability for its member countries even if none of them has a long history of stable prices and independent monetary policy as is the case in a number of monetary union initiatives among developing countries the positive effect obtains because the opportunistic objectives of one country s policy makers are kept in check at the union level by other members with disparate objectives we calibrate the model to evaluate the proposed monetary union in the east african community the empirical results show that the mutual restraint on monetary policy is an important determinant of the expected benefit from an eac monetary union

monetary integration in africa a deliberately european perspective abstract several initiatives for monetary integration in africa at the subregional level have recently emerged in terms of orthodox theory the preconditions are not satisfied and the sequencing of these initiatives appears at fault utilizing modern theories the paper examines the case for monetary integration which depends on the prospects for improved macro stability and surveys possible strategies by comparison with europe african countries seeking monetary integration have the advantage that they can peg to an appropriate external anchor external support for such a link perhaps from the european community would be an efficient and cost effective means of promoting such initiatives

technology adoption in the presence of network externalities we analyze technology adoption in industries where network externalities are significant the pattern of adoption depends on whether technologies are sponsored a sponsor is an entity that has property rights to the technology and hence is willing to make investments to promote it key findings include the following 1 compatibility tends to be undersupplied by the market but excessive standardization can occur 2 in the absence of sponsors the technology superior today has a strategic advantage and is likely to dominate the market 3 when one of two rival technologies is sponsored that technology has a strategic advantage and may be adopted even if it is inferior 4 when two competing technologies both are sponsored the technology that will be superior tomorrow has a strategic advantage

optimal contracting of separable production technologies abstract we analyze the class of agency problems with a risk neutral principal and a risk averse agent in which hidden actions and hidden information on the agent s efficiency are jointly present technological assumptions such as monotonicity of likelihood are no longer sufficient for the optimal contract to be monotone in the sharing rule we show that these regularity properties obtain for the rather wide class of production technologies that are separable in the agent s inputs together with ordinal properties such as monotone differences and affiliation of inputs separability yields the monotonicity in efficiency of the agent s actions and indirect utility

the benefits and costs of monetary union in southern africa a critical survey of the literature with the 14 members of the southern african development community sadc having set the objective of adopting a common currency for the year 2018 an expanding empirical literature has emerged evaluating the benefits and costs of a common currency area in southern africa this paper reviews that literature focusing on two categories of studies 1 those that assume that a country s characteristics are invariant to the adoption of a common currency and 2 those that assume that a monetary union alters an economy s structure resulting in trade creation and credibility gains the literature reviewed suggests that a relatively small group of countries typically including south africa satisfies the criteria necessary for monetary unification the literature also suggests that in a monetary union comprising all sadc countries and a regional central bank that sets monetary policy to reflect the average economic conditions e g fiscal balances in the region the potential losses i e higher inflation from giving up an existing credible national central bank a relevant consideration for south africa could outweigh any potential benefits of trade creation resulting from a common currency

graciela chichilnisky s model of north south trade abstract the model of the effects of north south trade set out by chichilnisky in the april 1981 issue of the journal of development economics is shown to contain a number of errors the model is presented anew in this note after corrections are made one can still obtain results similar in spirit to some of those chichilnisky tried to derive although the interpretation of the cause of the results must be substantially altered in particular it is shown that for appropriate parameter values in this model one will find that it is possible for an increase in the demand for the good the north exports to lead to 1 a worsening of the terms of trade for the south 2 a worsening of the distribution of factor incomes in the north and in the south 3 a reduction in the total export revenues of the south and 4 at the same time an increase in the physical volume of the south s exports the cause is in essence a shift in world demand from the good the south exports to the good the north exports which leads to a terms of trade loss for the south income effects following from the terms of trade loss then lead to a situation where the south s own demand for its export good falls by more than its supply thus leading to the preverse effect of an increase in the volume of its exports the paper also considers the model of chichilnisky and cole 1978 this model is similar to that of chichilnisky 1981 and is used to examine the same issues but is closed in a different way it is shown that this second model may give similar results as the first but that also a quite different set of results is now possible closure is therefore shown to play a key role

a discrete choice model with social interactions with an application to high school teen behavior we develop an empirical discrete choice interaction model with a finite number of agents we characterize its equilibrium properties in particular the correspondence between interaction strength number of agents and the set of equilibria and propose to estimate the model by means of simulation methods in an empirical application we analyze the individual behavior of high school teenagers in almost 500 school classes from 70 schools in our baseline model endogenous social interaction effects are strong for behavior closely related to school truancy somewhat weaker for behavior partly related to school smoking cell phone ownership and moped ownership and absent for behavior far away from school asking parents permission for purchases intra gender interactions are generally much stronger than cross gender interactions in a model with school specific fixed effects social interaction effects are insignificant with the exception of intra gender interactions for truancy copyright c 2007 john wiley sons ltd

selfish drug allocation for containing an international influenza pandemic at the onset recent epidemiologic studies have suggested that the prophylactic use of antiviral drugs could slow down the spread of an influenza epidemic because drug stockpiles are presently scattered in different countries the outbreak of an epidemic gives rise to a game in which each country must make decisions about how best to allocate its own stockpile in order to protect its population we develop a two period multivariate reed frost model to represent the spread of the epidemic within and across countries at its onset we consider the first two periods only to mimic the exponential growth of an epidemic in its early stage while keeping the model tractable preliminary numerical studies suggest that insights from the two period model hold in general when considering the entire time horizon our model captures three critical sources of uncertainty the number of initial infections the spread of the disease and drug efficacy we show that for small probabilities of between country infections the underlying game is supermodular nash equilibrium exists and there is a unique one that is pareto optimal among all existing equilibria further we identify sufficient conditions under which the optimal solution of a central planner such as the world health organization constitutes a pareto improvement over the decentralized equilibrium suggesting that countries should agree on an allocation scheme that would benefit everyone by contrast when the central planner s solution does not constitute a pareto improvement minimizing the total number of infected persons globally requires some countries to sacrifice part of their own population which raises intriguing ethical issues

improving policy credibility is there a case for african monetary unions abstract this paper analyzes experience with monetary policy in africa focusing on countries that have participated in rule based regional monetary agreements cfa zone east african currency board and rand monetary area we show that african countries have generally lacked the political institutions necessary for governments to commit credibly on an individual basis to financial stability we argue that monetary unions can provide an alternative means of credible commitment to sound macroeconomic policies but only under certain conditions first exit from a union must be made costly by the existence of parallel regional agreements and or links to the financial and technical assistance of industrial countries second governance structures of monetary unions must be designed so as to maximize chances for enforcement of monetary rules and third if a state seeks to break the rules of a union other member governments must actively oppose such attempts

choice interactions and business strategy choice settings are strategic to the extent that they entail cross sectional or intertemporal linkages these same factors may impose daunting demands on decision makers we develop a graph theoretic generalization of the nk model of fitness landscapes to model the way in which policy choices may be more or less strategic we use this structure to examine through simulation how fully articulated a strategy or set of policy choices must be to achieve a high level of performance and how feasible it is to offset past strategic mistakes through tactical adjustments instead of alignment our analysis highlights the role of asymmetry in the interaction of strategic choices and in particular the degree to which choices vary in terms of being influential dependent or autonomous from other choices

warrant exercise dividends and reinvestment policy in this paper we examine sequential exercise strategies by warrantholders and the gain from hoarding warrants we analyze several obstacles to acquiring large blocks in order to exploit sequential strategies first we identify several reinvestment policies for which sequential exercise is not advantageous thereby eliminating the gain from hoarding however sequential exercise strategies may be advantageous for monopoly or oligopoly warrantholders even absent dividends because using exercise proceeds to repurchase stock or to expand the firm s scale increases the riskiness of an equity share second oligopoly warrantholders can receive a smaller warrant value than perfectly competitive warrantholders suggesting a potential cost to unsuccessful hoarding

endogenous timing in the presence of non monotonicities the aim of this paper is to generalize the endogenous timing game proposed by hamilton and slutsky games and economic behavior 1990 2 pp 29 46 by allowing the payoff or the marginal payoff of a player to become non monotonic with respect to the strategy of the opponent we propose a taxonomy of the subgame perfect nash equilibria based on the characteristics of the payoff functions proposed by eaton canadian journal of economics 2004 37 pp 805 29 we determine under which conditions of the initial payoff functions commitment has a social value and when the simultaneous move nash equilibrium is commitment robust and discuss its pareto efficiency

lechatelier samuelson principle in games and pass through of shocks abstract the lechatelier samuelson principle states that as a reaction to a shock an agent s short run adjustment of an affected action is smaller than its long run adjustment when the agent can also adjust other related actions we extend the principle to strategic environments where the long run adjustment also accounts for other players adjusting their strategies we show that the principle holds for supermodular games strategic complements satisfying monotone comparative statics and provide sufficient conditions for the principle to hold in games of strategic substitutes heterogeneity we discuss the principle s implications for cost pass through of multiproduct firms

asymmetric information information externalities and efficiency the case of oil exploration in this article we examine the efect of private information and information externalities on the ex post eficiency of investment in oil exploration we show that too much drilling tends to occur ifjirms believe that the area is likely to contain a sizeable pool of oil and too little drilling occurs if the opposite is true bargaining with well defined property rights to the information externality can eliminate underinvestment but overinvestment remains a problem because firms have an incentive not to disclose their private information

optimism and pessimism in games this paper considers the impact of ambiguity in strategic situations it extends the earlier literature by allowing for optimistic responses to ambiguity ambiguity is modelled by ceu preferences we propose a new solution concept for players who may express ambiguitypreference then we study comparative statics of changes in ambiguity attitude in games with strategic complements this gives a precise statement of the impact of ambiguity on economic behaviour

on the adequacy of monetary arrangements in sub saharan africa we examine the economic rationale for monetary union s in sub saharan africa through the use of cluster analysis on a sample of 17 countries the variables used stem from the theory of optimum currency areas and from the fear of floating literature it is found that the existing cfa franc zone cannot be viewed as an optimum currency area cemac and uemoa countries do not belong to the same clusters and a core of the uemoa can be defined on economic grounds the results support the inclusion of the gambia ghana and sierra leone in an extended uemoa arrangement or the creation of a separate monetary union with the core of the uemoa and the gambia rather than the creation of a monetary union around nigeria finally the creation of the west african monetary zone wamz around nigeria is not supported by the data

a literature survey on proposed african monetary unions this study provides a survey of recent advances in the literature on proposed african monetary unions the survey comprises about 60 empirical papers published during the past fifteen years four main strands are discussed individually and collectively notably the proposed west african monetary zone wamz east african monetary union eamu southern african monetary union samu and african monetary union amu we observe a number of issues with establishing the feasibility and or desirability of potential monetary unions inter alia variations in choice of variables empirical strategies sampled countries and considered periodicities we address this ambiguity by reviewing studies with scenarios that are consistent with hegelian dialectics and establish selective expansion as the predominant mode of monetary integration some proponents make cases for strong pegs and institutions as viable alternatives to currency unions using cluster analysis disaggregating panels into sub samples and distinguishing shocks from responses in the examination of business cycle synchronisation provide more subtle policy implications we caution that for inquiries using the same theoretical underpinnings variables and methods just by modifying the scope context and periodicity may only contribute to increasing the number of conflicting findings authors should place more emphasis on new perspectives and approaches based on caveats of and lessons from the european monetary union emu and cfa zones

adoption externalities as public goods abstract a public good problem arises naturally in situations characterized by positive externalities or negative externalities for positive externalities agents furnish a public good by taking an action similarly for negative externalities agents furnish a public good by not taking an action we examine these externalities in a binary choice problem i e adoption externalities in each case there is a potential role for government intervention even when equilibrium transfers are not allowed since one equilibrium pareto dominates all others we analyze the positive and normative features of equilibria in these models and we explore the possibility of useful government intervention

north south trade and exported led policies abstract an earlier paper in this journal chichilnisky 1981 formulated a model of north south trade where the south exports a labor intensive commodity in exchange for industrial goods the paper studied moves to new equilibria with higher levels of exports of the south and of industrial demand in the north it was established that with abundant labor and technological dualism such moves lead to more exports but no lower terms of trade consumption and real wages in the south this occurs within walrasian stable and perfectly competitive markets sufficient conditions were also given for the south to improve its terms of trade real wages and consumption through an export expansion this paper comments on several other papers written on these results generalizes the earlier propositions and extends them to a larger class of economies which export labor intensive products but need not have abundant labor it gives a generalization of the earlier results on uniqueness and stability of the equilibria and reports also on recent econometric tests for sri lanka and the u k and numerical simulations of the model

rationalizability learning and equilibrium in games with strategic complementarities we study a rich class of noncooperative games that includes models of oligopoly competition macroeconomic coordination failures arms races bank runs technology adoption and diffusion r d competition pretrial bargaining coordination in teams and many others for all these games the sets of pure strategy nash equilibria correlated equilibria and rationalizable strategies have identical bounds also for a class of models of dynamic adaptive choice behavior that encompasses both best response dynamics and bayesian learning the players choices lie eventually within the same bounds these bounds are shown to vary monotonically with certain exogenous parameters we study the class of noncooperative supermodular games introduced by topkis 1979 and further analyzed by vives 1985 1989 who also pointed out the importance of these games in industrial economics supermodular games are games in which each player s strategy set is partially ordered the marginal returns to increasing one s strategy rise with increases in the competitors strategies so that the game exhibits strategic complementarity 2 and if a player s strategies are multidimensional marginal returns to any one com ponent of the player s strategy rise with increases in the other components this class turns out to encompass many of the most important economic applications of noncooperative game theory in macroeconomics diamond s 1982 search model and bryant s 1983 1984 rational expectations models can be represented as supermodular games in each of these models more activity by some members of the economy raises the returns to increased levels of activity by others in oligopoly theory some models of bertrand oligopoly with differentiated products qualify as supermodu lar games in these games when a firm s competitors raise their prices the marginal profitability of the firm s own price increase rises a similar structure is present in games of new technology adoption such as those of dybvig and spatt 1983 farrell and saloner 1986 and katz and shapiro 1986 when more users hook into a communication system or more manufacturers adopt an interface standard the marginal return to others of doing the same often rises similarly in some specifications of the bank runs model introduced by diamond and dybvig 1983 when more depositors withdraw their funds from a bank it is more worthwhile for other depositors to do the same in the warrant exercise

commodity prices and growth in africa a frican economies export primary commodities and most export little else policymakers as well as economists and historians of african economic development have seen these exports as both a hope and a curse the following parable tells the story once upon a time a servant of the ruler discovered a miraculous plant which grew readily in that country and whose seeds could be woven into fine cloth so desirable was this fabric that it became prized all over the world and fetched a high price after two score years the plant accounted for most of the country s trade with the world the ruler ordered the peasants to grow the plant paid them only a fraction of its price and he and his nobles became fabulously wealthy because the ruler wished to be remembered as a great ruler and as the father of his country he used his wealth to build a great army and brought machines from foreign countries to make the fine goods that previously could only be obtained from foreign merchants but the machines often broke down and the goods that they made were of poor quality and after the ruler died they were left to rust under the ruler s successor there was a war in a foreign land where the plant also grew so that there was a great shortage and its price increased threefold in only three seasons the new ruler spent his newfound riches on fantastic extravagance while immense sums were expended on public works after the manner of the east and on productive works carried out in the wrong way or too soon not even the threefold increase in prices could support these expenditures and the country soon found itself deeply in debt when the war ended and the price fell the country could no longer pay the interest on its debt or borrow more money even after it had sold its only useful public work to a foreign power so that power sent a mission to the country the publication of whose report from which the above

aggregation and imperfect competition on the existence of equilibrium we present a new approach to the theory of imperfect competition and apply it to study price competition among differentiated products the central result provides general conditions under which there exists a pure strategy price equilibrium for any number of firms producing any set of products this includes products with multi dimen sional attributes in addition to the proof of existence we provide conditions for uniqueness our analysis covers location models the characteristics approach and probabilistic choice together in a unified framework to prove existence we employ aggregation theorems due to prekopa 1971 and borell 1975 our companion paper caplin and nalebuff 1991 introduces these theorems and develops the application to super majority voting rules we present a new approach to the theory of imperfect competition and apply it to study price competition among differentiated products the central result is that there exists a pure strategy price equilibrium for any number of firms producing any set of products in addition to the proof of existence we provide conditions for uniqueness our model both unites diverse strands of the earlier literature and opens up uncharted areas for future analysis in particular we expand the traditional one dimensional framework to allow for multi dimen sional product differentiation our approach involves twin restrictions on consumer preferences one on individuals preferences the other on the distribution of preferences across society these are generalizations of the restrictions supporting 64 majority rule presented in caplin and nalebuff 1988 to prove existence we apply a new technique of aggregation this technique is valuable in a variety of other problems in the companion paper we use the aggregation result to generalize our earlier work on 64 majority rule and to characterize the relationship between the distribution of human capital and the distribution of income caplin and nalebuff 1991 there are additional applications in statistics and in search theory we begin with a brief review of the early literature on imperfect competition describing in more detail the existence problem and previous solutions section 3 presents our twin assumptions and shows that they cover many standard cases in section 4 we introduce the aggregation theorem and use it in the analysis of demand functions the proof of existence of equilibrium is in section

terms of trade and domestic distribution a comment abstract in a recent issue of this journal chichilnisky 1981 develops a north south two good static model to explore the implications of export led growth policies for the south s terms of trade and income distribution it is my contention that most of the results of this paper are invalid as stated furthermore i claim that the problems with these results are due in good part to mistakes when dealing with the elementary properties of the model namely existence uniqueness and stability of equilibria the first part of this note reviews these properties and the main results of chichilnisky 1981 are discussed in the final part