learning to believe in sunspots a number of authors have shown that competitive economies may possess sunspot equilibria that is rational expectations equilibria in which purely extrinsic uncertainty affects equilibrium prices and allocations 2 such results demonstrate that it does not require a lack of faith in the rationality of market participants to believe that competitive markets may be subject to purely speculative fluctuations driven solely by expectations 3 the mere existence of sunspot equilibria as solutions to a system of marketclearing conditions however might not be judged sufficient to indicate that competitive markets with rational participants could ever be subject to speculative instability the sunspot equilibria represent states of affairs in which agents act differently in the case of different realizations of the sunspot variable and it is rational for each agent to do so but it might be thought unlikely that the beliefs of all the participants in the market could ever come to be coordinated so as to bring about an equilibrium of that kind it is rational to believe that sunspots convey information about future states of affairs once the economy is in a sunspot equilibrium but why would rational agents ever begin to believe in such a thing so as to create the conditions under which the belief is rational in order to address such a question one must go beyond the mere statement of the conditions for equilibrium and discussion of what states of affairs satisfy them one must specify an explicit dynamic process according to which the beliefs of agents adjust when out of equilibrium any exercise of this kind is necessarily unsatisfactory as there is no univocal meaning for the postulate of rational behavior outside of an equilibrium it may well be the case that

on the existence of sunspot equilibria in an overlapping generations model abstract the existence of sunspot equilibria is shown in a one commodity overlapping generations model without stationarity assumptions on preferences endowments or nominal taxes the essential assumption is that there is a continuum of perfect foresight equilibria the technique is also useful for constructing stationary sunspot equilibria when they exist consumption in a sunspot equilibrium is shown to lie within the range consistent with perfect foresight

indeterminacy of stationary equilibrium in stochastic overlapping generations models abstract in this paper we consider the local uniqueness properties of stationary rational expectations equilibria ree in a stochastic overlapping generations olg model it is known that in non stochastic olg models steady state equilibria are locally isolated although there may exist indeterminate non stationary perfect foresight equilibria we show by construction that in the stochastic model even stationary equilibrium may be indeterminate we also show that this result is robust in the sense that there exists a non empty open set of economies for which the result is true

option pricing when the variance changes randomly theory estimation and an application in this paper we examine the pricing of european call options on stocks that have vari ance rates that change randomly we study continuous time diffusion processes for the stock return and the standard deviation parameter and we find that one must use the stock and two options to form a riskless hedge the riskless hedge does not lead to a unique option pricing function because the random standard deviation is not a traded security one must appeal to an equilibrium asset pricing model to derive a unique option pricing function in general the option price depends on the risk premium associated with the random standard deviation we find that the problem can be simplified by assuming that volatility risk can be diversified away and that changes in volatility are uncorrelated with the stock return the resulting solution is an integral ofthe black scholes formula and the distribution function for the variance of the stock price we show that accurate option prices can be computed via monte carlo simulations and we apply the model to a set of actual prices

models of stock returns a comparison in this paper a discrete mixture of normal distributions is proposed to explain the observed significant kurtosis fat tails and significant positive skewness in the distribution of daily rates of returns for a sample of common stocks and indexes stationarity tests on the parameter estimates of this discrete mixture of normal distributions model revealed significant differences in the mean estimates that can explain the observed skewness and significant differences in the variance estimates that can explain the observed kurtosis an alternative explanation for the observed fat tails is the symmetric student model the result of a comparison between the models is that the discrete mixture of normal distributions model has substantially more descriptive validity than the student model for many years both financial economists and statisticians have been concerned with the description of stock market returns the form of the distribution of stock returns is a crucial assumption for mean variance portfolio theory theoretical models of capital asset prices and the prices of contingent claims for example understanding the behavior of the variance is essential to option pricing models empirical tests of asset pricing models and the efficient markets hypothesis draw statistical inferences that are also conditional on distributional assumptions the most convenient assumption for financial theory and empirical methods is that the distribution of security rates of return be multivariate normal with parameters that are stationary over time since the normal distribution is stable under addition any arbitrary portfolio of stocks will also be normally distributed with the additional assumption of risk aversion mean variance theory follows furthermore the assumptions of normality and parameter stationarity are required for most of the econometric techniques typically used in empirical research tests of the normality hypothesis on the daily returns of the dow jones industrial stocks by fama 121 revealed more kurtosis fatter tails than that predicted from a sample of independent and identically distributed normal variates fama concluded from this evidence that the distribution of price changes conforms better to the stable paretian distribution with characteristic exponent

the pricing of options on assets with stochastic volatilities one option pricing problem that has hitherto been unsolved is the pricing of a european call on an asset that has a stochastic volatility this paper examines this problem the option price is determined in series form for the case in which the stochastic volatility is independent of the stock price numerical solutions are also produced for the case in which the volatility is correlated with the stock price it is found that the black scholes price frequently overprices options and that the degree of overpricing increases with the time to maturity one option pricing problem that has hitherto remained unsolved is the pricing of a european call on a stock that has a stochastic volatility from the work of merton 12 garman 6 and cox ingersoll and ross 3 the differential equation that the option must satisfy is known the solution of this differential equation is independent of risk preferences if a the volatility is a traded asset or b the volatility is uncorrelated with aggregate consumption if either of these conditions holds the risk neutral valuation arguments of cox and ross 4 can be used in a straightfoward way this paper produces a solution in series form for the situation in which the stock price is instantaneously uncorrelated with the volatility we do not assume that the volatility is a traded asset also a constant correlation between the instantaneous rate of change of the volatility and the rate of change of aggregate consumption can be accommodated the option price is lower than the blackscholes b s 1 price when the option is close to being at the money and higher when it is deep in or deep out of the money the exercise prices for which overpricing by b s takes place are within about ten percent of the security price this is the range of exercise prices over which most option trading takes place so we may in general expect the b s price to overprice options this effect is exaggerated as the time to maturity increases one of the most surprising implications of this is that if the b s equation is used to determine the implied volatility of a near the money option the longer the time to maturity the lower the implied volatility numerical solutions for the case in which the volatility is correlated with the stock price are also examined the stochastic volatility problem has been examined by merton 13 geske 7 johnson 10 johnson and shanno 11 eisenberg 5 wiggins 16 and

financial intermediation variability and the development process abstract in this paper we build a model of financial intermediation that explains the pattern of gdp variability in an economy during the development process we find evidence that per capita output is more volatile in middle income economies than in both low and high income economies we show that if the model economy is in the early or in the mature stages of development there is a unique equilibrium however in the middle stages of development multiple equilibria exist moreover we find that in economies with imperfect credit markets per capita output volatility tends to be higher than in economies with perfect or non existent credit markets

market distortions and local indeterminacy a general approach we provide a methodology to study the role of market distortions on the emergence of indeterminacy and bifurcations it consists in introducing general specifications for the elasticities of the crucial functions defining the aggregate equilibrium dynamics of the model this allows us to study how market distortions influence the range of values for the elasticity of input substitution under which local indeterminacy and bifurcations occur highlighting the main channels and classes of distortions responsible for indeterminacy most of the specific market imperfections considered in the related literature are particular cases of our framework comparing them we obtain several equivalence results in terms of local dynamic properties applying this methodology to the woodford 30 framework we find that distortions in the capital market per se do not play a major role we further show that for empirically plausible values of elasticity of substitution between inputs indeterminacy requires a minimal degree of distortions this degree seems to be high under output market distortions while with labor market distortions the required degree is empirically plausible

on monopolistic competition and involuntary unemployment in a simple temporary general equilibrium model it is shown that if the number of firms is small imperfect price competition in the markets for goods may be responsible for the existence of unemployment at any given positive wage in our examples involving two firms facing their true demand curves total monopolistic labor demand remains bounded as the wage rate goes to zero and unemployment prevails for a sufficiently large inelastic labor supply in the competitive case total labor demand would go to infinity and intersect labor supply at a positive wage

continuous time sunspot equilibria and dynamics in a model of growth abstract this article is concerned with the existence of sunspot equilibria in a continuous time growth setting it brings alternative approaches in the self fulfilling prophecies literature continuous time global dynamics and non stationarity the main contribution of the use of continuous time methods is to allow for a complete understanding of the global dynamical properties of these stochastic equilibria within a non stationary economy in this model fluctuations in growth rates occur through a self fulfilling prophecies mechanism journal of economic literature classification numbers e12 e32 o41

stationary sunspot equilibria in a finance constrained economy abstract stationary sunspot equilibria are shown to exist in a production economy with infinite lived agents when it is not possible to borrow against future wage income equilibrium fluctuations exhibit persistence over time scales of the same order of magnitude as observed business cycles an active fiscal policy that stabilizes aggregate money expenditures can prevent such fluctuations

determinacy of equilibrium in stationary economies with both finite and infinite lived consumers abstract we consider the determinacy of perfect foresight equilibrium near steady state equilibria of stationary infinite horizon economies the work of t j kehoe and d k levine econometrica 53 1985 433 453 is generalized by the inclusion of both infinite lived agents and overlapping generations of finite lived agents and the inclusion of production and non depreciating pure rents we show that indeterminacy is possible in robust examples and that the dimension of the indeterminacy can be as large as the number of goods per period we also discuss extreme cases in which determinacy is guaranteed

strategic complementarity in business formation aggregate fluctuations and sunspot equilibria the extent to which changes in beliefs can be important factors in initiating economic fluctuations has been a prominent area of investigation for macroeconomists the notion that beliefs about the future influence current decisions is a property of almost all dynamic economic systems the more challenging task is identifying economic environments in which changes in beliefs alone influence current choices in such a way that the variations in beliefs are self fulfilling because the resulting fluctuations arise in the absence of variations in fundamental variables such as preferences and technology they are often termed sunspot equilibria apart from suggesting that instability of expectations may be a distinct source of cyclical volatility sunspot equilibria may also explain why apparently small disturbances in fundamentals lead to large change in macroeconomic aggregates in this study we demonstrate the possibility of sunspot equilibria in an overlappinggenerations economy characterized by a plausible form of strategic complementarity as more agents enter as producers in any particular sector of the economy they create an incentive for agents to enter as producers into other sectors as well 2 the basis for this

information time option pricing theory and empirical evidence abstract with a stochastic time change from calendar time to information time we derive a parsimonious option pricing formula with stochastic volatility as a risk neutral poisson sum of merton s 1973 prices over the option s information time maturity domain the formula contains two unobservable parameters information arrival intensity and information time asset volatility with stochastic volatility induced by random information arrival when the information arrival rate intensifies the option price increases and vice versa we test the formula in pricing hedging and excess profits capture empirically using currency and the s p 500 futures options transaction data

uniqueness of an equilibrium in infinite horizon economies subject to taxes and externalities abstract this paper verifies the uniqueness of an equilibrium for a class of stochastic infinite horizon economies with capital that are subject to distortionary taxes or externalities the proof develops the property of concavity for a nonlinear monotone operator whose fixed points correspond to equilibria as the underlying monotone operator has been useful for establishing the existence of an equilibrium and for computing an equilibrium this approach also brings under one roof the study of existence uniqueness and approximation of an equilibrium in distorted economies journal of economic literature classification numbers c60 h20

involuntary unemplyment in imperfectly competitive general equilibrium models this paper is about involuntary unemployment in general equilibrium models with imperfect competition it surveys papers written after the seminal work of d aspremont dos santos ferreira and gerard varet 1984 this unemployment is called involuntary because it exists at any wage it results from imperfect competition in the product markets more specifically from firms excessive market power these papers have focussed their attention on the conditions required for involuntary unemployment in our presentation we characterise this form of unemployment through three elements consumers preferences price expectations and ford effects each element is important because it influences the demand for the good and hence its price elasticity the latter being central in the definition of firms market power jel classification d43 e24

increasing returns and animal spirits the purpose of this note is to simply point out that the multiplicity intrinsic of course to the presence of non convexities characterizes the models of growth with external increasing returns which have been studied recently and more importantly to show that the many competitive equilibria which often arise in those models can be interpreted as animal spirits equilibria that is equilibria indexed by the consumers optimism or pessimism this multiplicity of competitive equilibrium paths can be viewed as providing a new foundation upon which to build a theory of self fulfilling prophecies one which relies solely on the existence of external effects and does not rest on the overlapping generation structure or on back ward bending offer curves the conclusion that multiple animal spirits competitive equilibria are likely to arise in a model of external increasing returns would survive the generalization of the framework used in this paper to many period environments be they overlapping generation or representative agent infinite horizon structures this abstract was borrowed from another version of this item

stock price distributions with stochastic volatility an analytic approach we study the stock price distributions that arise when prices follow a diffusion process with a stochastically varying volatility parameter we use analytic techniques to derive an explicit closed form solution for the case where volatility is driven by an arithmetic ornstein ublenbeck or ar1 process we then apply our results to two related problems in the finance literature 1 options pricing in a world of stochastic volatility and 2 the relationship between stochastic volatility and the nature of fat tailes in stock price distributions article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

determinacy of equilibria in dynamic models with finitely many consumers abstract we consider a production economy with a finite number of heterogeneous infinitely lived consumers we show that if the economy is smooth enough equilibria are locally unique for almost all endowments we do so by converting the infinite dimensional fixed point problem stated in terms of prices and commodities into a finite dimensional negishi problem involving individual weights in a social value function by adding artificial fixed factors to utility and production functions we can write the equilibrium conditions equating spending and income for each consumer entirely in terms of time zero factor endowments and derivatives of the social value function

real business cycles and sunspot fluctuations are observationally equivalent abstract this paper points out that real business cycle models are observationally equivalent to externality models which we define as models with externalities and sunspots but without productivity shocks as far as standard first order systems are concerned however externality models turn out to be more flexible than rbc models this explains at least partly why previous studies have found that externality models perform better than standard rbc models at generating realistic business cycle behavior our results cast doubt on the arguments of farmer and guo 1994 and caballero and lyons 1992

stabilizing competitive business cycles abstract we study how stylized monetary proportional money transfers fiscal lump sum money transfers and public expenditure policies may eliminate endogenous deterministic cycles and stationary markov sunspot equilibria in a simple version of the overlapping generations model we also present new constructive methods for analyzing stationary markov sunspot equilibria in such a framework

non linear dynamics in the infinite time horizon model there are two important reasons why economic growth theory became again a popular field during the last 15 years the first one is that recently developed growth theoretic models capture more aspects of economic growth than the models used in the fifties and sixties nowadays models of economic growth try to explain technological progress and innovations whereas the purpose of traditional models was mainly to describe the process of capital accumulation

consumer confidence and economic fluctuations if consumers become pessimistic about the state of the economy can there be a slowdown in output even if their pessimism is not based on economic fundamentals recent macroeconomic models show the answer is yes if there are strategic complementarities and multiple equilibria we investigate the link between consumer confidence and economic fluctuations using vector autoregressions in all models after controlling for economic fundamentals the hypothesis that consumer sentiment does not cause gnp in the granger sense can be rejected variance decompositions suggest that consumer sentiment accounts for between 13 and 26 percent of the innovation variance of gnp

economies of scale in banking indeterminacy and monetary policy this paper investigates economies of scale es in financial intermediation as a source of equilibrium indeterminacy consumption in the model can be purchased with currency and deposits and es in intermediation implies that deposit costs are decreasing in aggregate deposits the results suggest that indeterminacy does not depend on a large degree of es nor a large intermediation sector but on monetary policy and the determination of nominal interest rates monetary policies not targeting nominal rates allow for indeterminacy to arise for any degree of es while policies targeting nominal rates eliminates indeterminacy for all degrees of es

indeterminacy and endogenous fluctuations in two sector growth models with externalities abstract this paper discusses the influence of technological externalities on the dynamic properties of accumulation paths in a two sector growth model in discrete time following the recent paper of boldrin and rustichini 1994 in which the authors study indeterminacy in a particular case we first provide some necessary and or sufficient conditions for the indeterminacy of equilibria in the general two sector model we also provide some conditions for the existence of period two cycles when equilibria are indeterminate we prove finally that depending on the nature of externality indeterminacy may lead to the existence of quasi periodic paths

on jump processes in the foreign exchange and stock markets exchange rates exhibit systematic discontinuities even after allowingfor conditional heteroskedasticity in the diffusion process the results are much more significant in theforeign exchange market than in the stock market which suggests differences in the structure of these markets finally this jump component is shown to explain some of the empirically observed mispricings in the currency options market the objective of this article is to analyze and compare the empirical distribution of returns in the stock market and in the foreign exchange market there are a number of reasons why a better understanding of the stochastic processes driving prices in these markets would be useful many financial models rely heavily on the assumption of a particular stochastic process while relatively little attention is paid to the empirical fit of the postulated distribution as a result models like option pricing models are applied indiscriminately to various markets such as the stock market and the foreign exchange market when the underlying processes may be fundamentally different the foreign exchange market for instance is characterized by active exchange rate man

growth externalities and sunspots abstract in this paper we consider a simple model of neo classical capital accumulation with production externalities in which a continuum of identical infinitely lived agents produce output from a standard stationary neo classical production technology and choose their actions to maximize a discounted sum of single period utilities because of the presence of the externality in production the model exhibits sunspot equilibria

there may be unemployment when the labour market is competitive and the output market is not is unemployment always caused by union power or more generally downwards rigidity of wages the influential article by hart i 982 says yes there cannot be unemployment unless labour unions prevent wages from falling the more recent papers by d aspremont et al i 984 i989 a b and by dehez i 985 say no unemployment may occur when the labour market is perfectly competitive and the output market is not all this work assumes a fixed labour supply but the more recent models significantly depart from hart s formulation in other respects 2 one may ask which answer is the robust one this paper shows that hart s answer is based on a facilitating assumption on marginal revenue i replace it by a more realistic hypothesis and replicate hart s existence and comparative statics results except that now unemployment may occur when the labour market is perfectly competitive and the output market is not more precisely there can be unemployment at any nonnegative wage and perfect competition in the labour market may generate zero wages and unemployment labour becoming a free good in excess supply a useful costless resource is then wasted away and thus a gross form of inefficiency occurs in hart i982 on the contrary perfect competition in the labour market necessarily yields full employment and pareto efficiency labour does not often become a free good in excess supply in modern industrial economies but this possibility may help explain why labour markets have become noncompetitive wages are positive at an overall walrasian equilibrium but imagine that the output markets become oligopolistic and as a result the perfectly competitive wage drops to zero workers are now severely exploited in the sense of joan robinson i933 ch 25 and pigou i920 because the real wage is lower than the physical marginal product of labour unionisation can then be seen as providing countervailing power in

tests of an american option pricing model on the foreign currency options market this paper tests the ability of the american option pricing model proposed by parkinson 18 or mason 14 to explain the pricing of the foreign currency options traded on the philadelphia stock exchange from february 28 1983 to march 26 1985 we find that the model underprices out of the money options relative to at the money and in the money options this relative underpricing is driven by an underpricing of out of the money call options of short maturity in addition the degree of relative mispricing for most categories of options is shown to be a decreasing function of the time to maturity of the options longer maturity options appear to trade at similar levels of implied volatility whether they are in at or out of the money most of these biases appear consistent with the fact that the underlying spot currency rate follows a mixed jump diffusion process as described in 17

quadratic variation based dynamic strategies the paper analyzes a family of dynamic trading strategies which do not rely on any stochastic process assumptions aside from continuity and positivity and in particular do not require predicting future volatilities derivative payoffs can still be replicated except that this occurs at the stopping time at which the realized cumulative squared volatility hits a predetermined level the application of these results to portfolio insurance is emphasized and hedging strategies studied by black and jones and by brennan and schwartz are generalized classical results on european style options arise as special cases for example the initial cost of replicating a call or a put under the new method is given by a generalized black scholes formula which yields the ordinary black scholes formula when the volatility is derterministic

option values under stochastic volatility theory and empirical estimates abstract this paper numerically solves the call option valuation problem given a fairly general continuous stochastic process for return volatility statistical estimators for volatility process parameters are derived and parameter estimates are calculated for several individual stocks and indices the resulting estimated option values do not differ dramatically from black scholes values in most cases although there is some evidence that for longer maturity index options black scholes overvalues out of the money calls in relation to in the money calls

a model of imperfect competition with keynesian features the recent literature on the reappraisal of keynes has viewed keynesian equilibria as arising when prices are fixed and effective demands and supplies are equilibrated through the adjustment of quantities one problem with this approach is that it lacks a theory of price determination in particular of why prices are fixed in the present paper we show that a number of keynesian features arise in a model in which prices are fully flexible but where agents have some monopoly power one advantage of this approach is that it provides a theory of the determination of both prices and quantities

symmetric smooth consumption externalities abstract based on arrow s model of a pure exchange economy with smooth consumption externalities this paper studies how the internalization of external effects through a network of markets between agents introduces symmetry breakings in the set of equilibria it shows indeed how identical agents can be treated asymmetrically by complete markets this work emphasizes that equilibrium allocations may be very sensitive to the way coase type rights are distributed journal of economic literatureclassification numbers d50 d62 h23 k11

a class of asset pricing models governed by subordinate processes that signal economic shocks abstract we consider a mean reverting risk neutral short rate process model with a vector of subordinated drift processes that accounts for the random effect of the arrival of new information it is assumed that the market is efficient with no arbitrage opportunities closed form expressions for the price in nominal and in real terms of a discount bond are obtained we define a risk neutral exchange rate model with correlated subordinated drift and volatility processes that reflect the effect of the arrival of new information pertaining to the countries involved the cases of complete and incomplete exchange markets with no arbitrage opportunities are considered

the economic determinants of technology shocks in a real business cycle model abstract creative destruction due to new technologies causes both long run growth and short run business fluctuations new technologies push the economy on a higher productivity level but also imply partial obsolescence of old production units obsolescence induces an adjustment period during which growth rates gradually fall at some endogenously determined point research for the next technology starts once the new technology is discovered a technology shock occurs and the next cycle starts this is shown in a continuous time rbc model with risk averse agents where savings can be used for financing deterministic capital accumulation and stochastic r d for new technologies

rational random walks the paper examines within the framework of a multi dimensional one step forward looking model a special category of rational expectations equilibria their support is infinite with two accumulation points steady states the stochastic motion of the system is of random walk type a general strategy for an existence proof associated with the study of a dynamical systemstresses necessary conditions in a simple overlapping generations model the proof is made complete no backwards bending labour supply is required in the pure sunspot case by continuity heteroclinic random walk equilibria are also shown to exist when shocks are real i introduction many economic models consider exogenous variables that follow stochastic processes of a random walk type the present paper considers a category of rational expectation equilibria in which the path of endogenous variables exhibits a similar qualitative feature the state of the system walks randomly furthermore this random walk takes place between two steady states of the system we call such equilibria random walk because of the temporal stochastic process followed by the equilibrium state heteroclinic because the support of the process connects two steady states in the state space equilibria the paper defines and discusses such equilibria and proposes a general methodology for assessing their existence it shows on a simple example that they do exist they may be either of sunspot type in the case where fluctuations are driven by beliefs only or extrinsic in cass shell 1983 terminology or non sunspot when some underlying fundamentals actually follow a random walk although the study has an exploratory dimension it strongly suggests that the random walk rational expectation equilibria under scrutiny exist within a large class of models in particular an explicit example of sunspot random walk equilibria is exhibited in a subclass of overlapping generations models that do not have traditional sunspot equilibria i e sunspot equilibria triggered by stationary markov processes finally when

strategic complementarity slows macroeconomic adjustment to temporary shocks i introduction starting with the work of diamond 1982 hart 1982 and bryant 1983 a number of authors have employed models which use potential coordination failure to show that many features of the keynesian framework can be captured in models consistent with the microfoundations approach 1 for example in the context of a search model diamond demonstrates the existence of equilibria with too low a level of aggregative activity hart captures this feature and the simultaneous existence of multipliers in a model of monopolistic competition while technological interactions are the crucial element of bryant s analysis one reason to refer to these seemingly diverse set of papers as a single literature is that all the models are in fact driven by the presence of the same factor strategic complementarity a macroeconomic model which exhibits strategic complementarity is simply one where the larger is aggregate production the larger is the incentive for any particular agent to produce cooper and john 1988 first demonstrated that the presence of strategic complementarity is a characteristic of all of the models mentioned above and persuasively argue that this is the critical feature which lies behind the finding of keynesian type results in this paper we argue that strategic complementarity is also important in understanding the dynamic response of economies to temporary shocks in particular we find that strategic complementarity is potentially an important factor in understanding why an economy may return only slowly to steady state behavior after a temporary shock that is given the presence of any of a variety of factors which would cause the economy not to instantaneously return to full employment after a temporary shock e g adjustment costs associated with changing the capital stock the speed with which the economy returns to steady state behavior is negatively related to the degree of strategic complementarity in the environment related analyses are those of haltiwanger and waldman 1989 bomfim and diebold 1992 and baxter and king 1990 the first two papers consider models wherein some agents are characterized by adaptive or regressive expectations while others am characterized by rational expectations among other findings these analyses demonstrate that the speed with which the economy returns to steady state behavior after a temporary shock is negatively related to the degree of strategic complementarity in the economy 2 we argue that the relationship between strategic complementarity and the dynamic response to temporary shocks is more general than is suggested by these papers in their analyses temporary shocks have long term effects because some of the agents make systematic mistakes when forming expectations here it is argued that given any of a variety of factors which would cause temporary shocks to have long term effects there is a negative relationship between adjustment speed and the degree of strategic complementarity baxter and king consider a world where because of productive externalities the economy exhibits increasing returns at the economy wide level using simulation techniques they show first that the presence of increasing returns serves to increase the output volatility exhibited by the economy in response to shocks and second that after a one time shock the return to steady state behavior is slower in a world characterized by increasing returns baxter and king do not discuss their results in terms of strategic complementarity however it is easy to show that one way of introducing strategic complementarity is to assume that the economy exhibits increasing returns at the economy wide level our paper suggests that what is central in baxter and king s study is not the introduction of increasing returns per se but rather that the introduction of increasing returns is one way of introducing strategic complementarity that is baxter and king s findings can be thought of as a manifestation of the central point of the current paper

valuation of american futures options theory and empirical tests this paper reviews the theory of futures option pricing and tests the valuation principles on transaction prices from the s p 500 equity futures option market the american futures option valuation equations are shown to generate mispricing errors which are systematically related to the degree the option is in the money and to the option s time to expiration the models are also shown to generate abnormal risk adjusted rates of return after transaction costs the joint hypothesis that the american futures option pricing models are correctly specified and that the s p 500 futures option market is efficient is refuted at least for the sample period january 28 1983 through december 30 1983 futures option contracts now trade on every major futures exchange and on a wide variety of underlying futures contracts the chicago mercantile exchange the chicago board of trade the new york futures exchange and the commodity exchange now collectively have more than twenty options written on futures contracts where the underlying spot commodities are financial assets such as stock portfolios bonds notes and eurodollars foreign currencies such as west german marks swiss francs and british pounds precious metals such as gold and silver livestock commodities such as cattle and hogs and agricultural commodities such as corn and soybeans moreover new contract applications are before the commodity futures trading commission and should be actively trading in the near future with the markets for these new contingent claims becoming increasingly active it is appropriate that the fundamentals of futures option valuation be reviewed and tested black 5 provides a framework for the analysis of commodity futures options although his work is explicitly directed at pricing european options on forward contracts it applies to european futures contracts as well if the riskless rate of interest is constant during the futures option life 1 the options currently

a dynamic equilibrium model of asset prices and transaction volume a dynamic general equilibrium model of capital asset pricing is constructed in which the volume of capital traded is determined endogenously the model also gives rise to a novel asset pricing formula it is shown that temporary shocks can give rise to serially correlated changes in the price of capital and transaction volume that persist long after the initial disturbance the frequency and amplitude of the resulting cycles are related to the length of the agent s planning horizon and the discount factor the model s implications for explaining asset price volatility are also explored

general equilibrium pricing of options on the market portfolio with discontinuous returns when the price process for a long lived asset is of a mixed jump diffusion type pricing of options on that asset by arbitrage is not possible if trading is allowed only in the underlaying asset and a risk less bond using a general equilibrium framework we derive and analyze option prices when the underlying asset is the market portfolio with discontinuous returns the premium for the risk of jumps and the diffusion risks forms a significant part of the prices of the options in this economy an attempted replication of call and put options by the black scholes type of trading strategies may require substantial infusion of funds when jumps occur we study the cost and risk implications of such dynamic hedging plans article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

an overlapping generations model of growth and the environment this article analyzes the potential conflict between economic growth and the maintenance of environmental quality in an overlapping generations model short lived individuals make decisions which have long lasting effects on both factor productivity and the environment the model provides a theoretical explanation of observed correlations between environmental quality and income whereby economic growth is associated first with declines then improvements in environmental quality it suggests circumstances in which multiple pareto ranked steady state equilibria may arise and in which sustained growth of both capital and environmental quality may occur overmaintenance of the environment analogous to dynamically inefficient overaccumulation of capital may emerge copyright 1994 by royal economic society

modeling the bid ask spread measuring the inventory holding premium the need to understand and measure the determinants of market maker bid ask spreads is crucial in evaluating the merits of competing market structures and the fairness of market maker rents this study develops a simple parsimonious model for the market maker s spread that accounts for the effects of price discreteness induced by minimum tick size order processing costs inventory holding costs adverse selection and competition the inventory holding and adverse selection cost components of spread are modeled as an option with a stochastic time to expiration this inventory holding premium embedded in the spread represents compensation for the price risk borne by the market maker while the security is held in inventory the premium is partitioned in such a way that the inventory holding and adverse selection cost components as well as the probability of an informed trade are identified the model is tested empirically using nasdaq stocks in three distinct minimum tick size regimes and is shown to perform well both in an absolute sense and relative to competing specifications

stable multilateral trade agreements we analyse multilateral tariff negotiations as a game in coalition form in a model with three identical countries that produce and trade an homogeneous commodity and where countries aggregated welfare can weight differently their different components we analyse how changes in the countries objective affects the stability of coalitions in other words we characterize what tariff agreements if any are stable i e lie in the core

the price variability volume relationship on speculative markets this paper concerns the relationship between the variability of the daily price change and the daily volume of trading on the speculative markets our work extends the theory of speculative markets in two ways first we derive from economic theory the joint probability distribution of the price change and the trading volume over any interval of time within the trading day and second we determine how this joint distribution changes as more traders enter or exit from the market the model s parameters are estimated by fiml using daily data from the 90 day t bills futures market the results of the estimation can reconcile a conflict between the price variability volume relationship for this market and the relationship obtained by previous investigators for other speculative markets this paper concerns the relationship between the variability of the daily price change and the volume of trading on speculative markets previous empirical studies 2 3 6 12 14 16 of both futures and equity markets always find a positive association between price variability as measured by the squared price change ap2 and the trading volume 2 there are two explanations for the relationship clark s 2 explanation which is secondary to his effort to explain why the probability distribution of the daily price change is leptokurtic emphasizes randomness in the number of within day transactions in clark s model the daily price change is the sum of a random number of within day price changes the variance of the daily price change is thus a random variable with a mean proportional to the mean number of daily transactions clark argues that the trading volume is related positively to the number of within day transactions and so the trading volume is related positively to the variability of the price change the second explanation is due to epps and epps 6 their model examines the mechanics of within day trading the change in the market price on each within day transaction or market clearing is the average of the changes in all of the traders reservation prices epps and epps assume there is a positive relationship between the extent to which traders disagree when they revise their reservation prices and the absolute value of the change in the market price that is an increase in the extent to which traders disagree is associated with a larger absolute price change the price variability volume relationship arises then because the volume of trading is positively related to the extent to which traders disagree when they revise their reservation prices