can portmanteau nonlinearity tests serve as general mis specification tests a number of recent papers have employed the bds test as a general test for mis specification for linear and nonlinear models we show that for a particular class of conditionally heteroscedastic models the bds test is unable to detect a common mis specification our results also demonstrate that specific rather than portmanteau diagnostics are required to detect neglected asymmetry in volatility however for both classes of tests reasonable power is only obtained using very large sample sizes

testing for nonlinear dependence in daily foreign exchange rates the purpose of this article is to investigate whether daily changes in five major foreign exchange rates contain any nonlinearities although the data contain no linear correlation evidence indicates the presence of substantial nonlinearity in a multiplicative rather than additive form further examination reveals that a generalized autoregressive conditional heteroskedasticity model can explain a large part of the nonlinearities for all five exchange rates copyright 1989 by the university of chicago

answering the skeptics yes standard volatility models do provide accurate forecasts a voluminous literature has emerged for modeling the temporal dependencies in financial market volatility using arch and stochastic volatility models while most of these studies have documented highly significant in sample parameter estimates and pronounced intertemporal volatility persistence traditional ex post forecast evaluation criteria suggest that the models provide seemingly poor volatility forecasts contrary to this contention we show that volatility models produce strikingly accurate interdaily forecasts for the latent volatility factor that would be of interest in most financial applications new methods for improved ex post interdaily volatility measurements based on high frequency intradaily data are also discussed

nonlinear nonparametric nonessential exchange rate estimation a wide variety of empirical exchange rate mo dels have been estimated over the years but despite the considerable energies that have been devoted to this work the economics profession has remarkably little to show for itself there is little evidence that conclusively links the bilateral exchange rates of typical oecd countries to fundamental macroeconomic determinants of exchange rates such as money output relative prices or interest differentials coefficient estimates are notoriously unstable and frequently mis signed compared with theoretical predictions exchange rate equations do not fit particularly well and forecast no better than the simplest naive alternatives recently a new class of exchange rate models was introduced by paul krugman 1988 these models provide a potential reason for the poor performance of traditional exchange rate models because they are nonlinear if the exchange rate actually depends in a nonlinear way on exogenous macroeconomic fundamentals linear exchange rate models may work poorly even though the exchange rate is closely linked to fundamentals in this paper we provide a brief sketch of some of this work as well as some preliminary evidence on the actual performance of these nonlinear models in our empirical analysis we use a nonparametric estimator that can handle a wide variety of nonlinear phenomena we examine fixed exchange rate regimes where nonlinearities should be quite easy to detect however we do not find strong empirical support for the hypothesis that the incorporation of nonlinear effects significantly improves models of exchange rate determination in section i we briefly review the theoretical literature on nonlinear target zone exchange rate models linking this work to the tests for intrinsic bubbles we draw heavily on recent papers by kenneth froot and maurice obstfeld 1989a b our methodology and data are discussed in section ii section iii contains new empirical tests for nonlinearities in exchange rate models

the effect of asymmetries on optimal hedge ratios there is widespread evidence that the volatility of stock returns displays an asymmetric response to good and bad news this article considers the impact of asymmetry on time varying hedges for financial futures an asymmetric model that allows forecasts of cash and futures return volatility to respond differently to positive and negative return innovations gives superior in sample hedging performance however the simpler symmetric model is not inferior in a hold out sample a method for evaluating the models in a modern risk management framework is presented highlighting the importance of allowing optimal hedge ratios to be both time varying and asymmetric

time irreversibility and egarch effects in us stock index returns in this paper we suggest using a modified version of the time reversibility tr test of chen chou and kuan 2000 as a complementary diagnostic test for time series models the modified cck test is easy to compute and requires weaker moment conditions than existing tests our simulations demonstrate that this test is powerful against asymmetry in volatility but the bds test is not in the empirical study of us stock index returns we first find that these returns are all time irreversible applying the garch and egarch models to these returns we also find that the q and bds tests always accept the null hypothesis and cannot distinguish between these models by contrast the modified cck test accepts only the egarch model with an order that can accommodate the underlying asymmetry in volatility our results suggest that the detected time irreversibility in these return series may be attributed to volatility asymmetry and that such asymmetry may be captured using a proper egarch model copyright 2002 john wiley sons ltd

cross sectional estimation of fdi spillovers when fdi is endogenous ols and iv estimates for mexican manufacturing industries cross sectional estimates of foreign direct investment fdi spillovers are biased when the variable capturing the cross industry variation of foreign participation is endogenous to the estimated regression model in this article i introduce an original instrument for this problematic fdi variable capturing the general fdi intensity of manufacturing industries i use this instrument to estimate fdi externalities in a cross section of mexican manufacturing industries the main findings show that in contrast to the common criticism that ordinary least squares ols estimation produces an upward bias in the estimated fdi externality effect for the sample of mexican manufacturing industries ols estimation causes a downward bias controlling for the tendency among foreign manufacturing firms to gravitate towards low productivity industries the instrumental variable estimations provide robust evidence of significantly larger positive fdi spillover effects

nonlinearity and intraday efficiency tests on energy futures markets using high frequency data this paper first time comprehensively examines the intraday efficiency of four major energy crude oil heating oil gasoline natural gas futures markets in contrast to earlier studies which focus on in sample evidence and assume linearity the paper employs various nonlinear models and several model evaluation criteria to examine market efficiency in an out of sample forecasting context overall there is evidence for intraday market inefficiency of two of the four energy future markets heating oil and natural gas which exists particularly during the bull market condition but not during the bear market condition the evidence is also robust against the data snooping bias and the model overfitting problem and its economic significance can be very substantial

the statistical properties of daily foreign exchange rates 1974 1983 abstract this paper examines the statistical properties of daily rates of change of five foreign currencies from 1974 to 1983 the main purpose is to discriminate between two competing explanations for the observed heavy tails of the distribution that the data are independently drawn from a heavy tail distribution which remains fixed over time and that the data come from distributions which vary over time evidence point to the rejection of the first hypothesis further investigations show that the rejection can be attributed to changing means and variances in the data which can be described by a simple statistical model

monopoly provision of product quality and warranties an exploration in the theory of multi dimensional screening we address the monopoly problem of designing and pricing a product line of goods distinguished by different quality and warranty levels consumers vary in their evaluations of these attributes so that the problem is one of screening it is sufficiently complex that the local approach commonly used does not work instead we use new techniques for dealing with incentive constraints between nonadjacent consumer types these techniques allow us to characterize optimal allocations that may not be monotonic in particular although the more eager types of buyer do pay higher prices and yield the monopoly higher profit they may receive lower quality or lower warranty coverage we find preference restrictions that restore monotonicity concave risk tolerance implies that warranty coverage increases in type and constant absolute risk aversion implies that quality increases in type

nonlinear dynamics in financial markets evidence and implications daily asset returns exhibit two key statistical properties price changes are not autocorrelated but the absolute values of changes are strongly autocorrelated nonlinear processes can generate this type of behavior linear processes cannot additively nonlinear processes are consistent with the view that expected returns are time varying although much effort has been applied to modeling expected returns there has been little evidence to support the view that time varying expected returns can account for the strong nonlinearity in the observed returns data multiplicatively nonlinear models are consistent with the view that expected volatilities are time varying evidence from price changes as well as options implied volatilities show that volatility is time varying and mean reverting in fact multiplicatively nonlinear models have been able to explain a great deal of the nonlinearity in asset returns thus future volatility can be forecast even though the direction of price changes is difficult

the statistical distribution of exchange rates empirical evidence and economic implications the abundant evidence that changes in exchange rates have distributions with fatter tails than the normal distribution has led researchers to consider non normal distributions including the student the stable paretian and mixtures of distributions this paper compares the empirical fits of three non normal candidates and the normal distribution for daily changes in the logarithms of exchange rates using maximum likelihood estimation of the parameters and chi square goodness of fit tests the student and mixture of two normals provide the best fits but there is evidence that the distribution parameters may vary over time

optimal collusion resistant mechanisms with verification abstract we present the first general positive result on the construction of collusion resistant mechanisms that is mechanisms that guarantee dominant strategies even when agents can form arbitrary coalitions and exchange compensations sometimes referred to as transferable utilities or side payments this is a much stronger solution concept as compared to truthful or even group strategyproof mechanisms and only impossibility results were known for this type of mechanisms in the classical model we describe collusion resistant mechanisms with verification that return optimal solutions for a wide class of mechanism design problems which includes utilitarian ones as a special case note that every collusion resistant mechanism without verification must have an unbounded approximation factor and in general optimal solutions cannot be obtained even if we content ourselves with truthful non collusion resistant mechanisms all these results apply to problems that have been extensively studied in the algorithmic mechanism design literature like for instance task scheduling and inter domain routing

nonlinear dynamics and stock returns simple deterministic systems are capable of generating chaotic output that mimics the output of stochastic systems for this reason algorithms have been developed to distinguish between these two alternatives these algorithms and related statistical tests are also useful in detecting the presence of nonlinear dependence in time series in this article the authors apply these procedures to stock returns and find evidence that indicates the presence of nonlinear dependence on weekly returns from the center for research in security prices value weighted index copyright 1989 by the university of chicago

when are local incentive constraints sufficient we study the question of whether local incentive constraints are sufficient to imply full incentive compatibility in a variety of mechanism design settings allowing for probabilistic mechanisms we give a unified approach that covers both continuous and discrete type spaces on many common preference domains including any convex domain of cardinal or ordinal preferences single peaked ordinal preferences and successive single crossing ordinal preferences local incentive compatibility suitably defined implies full incentive compatibility on domains of cardinal preferences that satisfy a strong nonconvexity condition local incentive compatibility is not sufficient our sufficiency results hold for dominant strategy and bayesian nash solution concepts and allow for some interdependence in preferences

costly distortion of information in agency problems anecdotal evidence suggests that agents often spend resources distorting information transmitted to principals we present a model where costly information distortion emerges as equilibrium behavior the information structure we focus on is intermediate between and encompasses the cases of private information and public information the agent can falsify the privately observed state at some cost although the principal can design contracts that induce no falsification these may involve excessive iinformation rents falsification can be beneficial in spite of the waste of resources involved because it helps reduce information rents we examine how optimal contract and equilibrium payoffs change as the information structure ranges from private to public information

implications of nonlinear dynamics for financial risk management this paper demonstrates that when log price changes are not iid their conditional density may be more accurate than their unconditional density for describing short term behavior using the bds test of independence and identical distribution daily log price changes in four currency futures contracts are found to be not iid while there appear to be no predictable conditional mean changes conditional variances are predictable and can be described by an autoregressive volatility model that seems to capture all the departures from independence and identical distribution based on this model daily log price changes are decomposed into a predictable part which is described parametrically by the autoregressive volatility model and an unpredictable part which can be modeled by an empirical density either parametrically or nonparametrically this two step seminonparametric method yields a conditional density for daily log price changes which has a number of uses in financial risk management

partially verifiable information and mechanism design in a principal agent model with adverse selection we study the implementation of social choice functions when the agent s message space is a correspondence which depends on this true characteristic we characterize such correspondence for which the revelation principle is valid returns must not contradict easily observable elements of the taxpayer s lifestyle in this paper we present a model of two person organizations in which these considerations are important we ask whether the restrictions on fallacious statements inherent in the system are sufficient to achieve the goals of the organization we show that the optimal way of eliciting the agent s response may not be to establish incentives for truthtelling in all instances in our model there is one player the agent who observes the state of the economic system another player the principal takes an action based on the information presented to him by the agent this class of models is often referred to as the principal agent problem in the extensive and growing literature on this problem it has always been assumed that the agent could lie to the principal and therefore that he had to be properly motivated to act at least partially in the principal s interest our formal way of modelling the partial verifiability of information is to introduce the restriction that the agent s responses must lie in a set m o that varies with the true state 0 it is assumed that this set always admits the possibility of responding with the true state the way in which the allowable response set varies with the true state is known to the principal in other respects we retain the usual principal agent formalization in particular the principal is the stackelberg leader in this game he can commit himself to choose a collective action as a function of the message transmitted by the agent whether the variation of the message space with the true observation is purely technological or whether it is induced by the severity of potential actions of the principal

the conditional heteroscedasticity of the yen dollar exchange rate this paper examines the conditional heteroscedasticity of the yen dollar exchange rate a model is constructed by extending the asymmetric power autoregressive conditional heteroscedasticity model to a process that is fractionally integrated it is found that unlike the equity markets the appreciation and depreciation shocks of the yen against the dollar have similar effects on future volatilities although the results reject both the stable and the integrated models our analysis of the response coefficients of the past shocks and the application of the models to the estimation of the capital requirements for trading the currencies show that there are no substantial differences between the fractionally integrated models and the stable models 1998 john wiley sons ltd

accurate minimum capital risk requirements a comparison of several approaches in this paper we estimate for several investment horizons minimum capital risk requirements for short and long positions using the unconditional distribution of three daily indexes futures returns and a set of short and long memory stochastic volatility and garch type models we consider the possibility that errors follow a t student distribution in order to capture the kurtosis of the returns series the results suggest that accurate modelling of extreme observations obtained for long and short trading investment positions is possible with an autoregressive stochastic volatility model moreover modelling futures returns with a long memory stochastic volatility model produces in general excessive volatility persistence and consequently leads to large minimum capital risk requirement estimates finally the models predictive ability is assessed with the help of out of sample conditional tests

forward and futures prices evidence from the foreign exchange markets empirical studies of the treasury bill markets have revealed substantial differences between the futures price and the implied forward price these differences have been attributed to taxes transaction costs and the settling up procedure employed in the futures market this paper examines the forward and futures prices in foreign exchange in an attempt to distinguish between the competing explanations empirical studies of the treasury bill market have revealed differences between the futures price or rate and the implicit forward price derived from the term structure of interest rates 1 these differences have generally been attributed to market imperfections such as taxes and transaction costs see for example arak 1 capozza and cornell 2 and rendelman and carabini 6 recently however cox ingersoll and ross 3 henceforth cir derived a model in which forward and futures prices need not be equal even in perfect markets without taxes as long as interest rates are stochastic the significance of the cir effect may be hard to investigate using only data from the bill market because of the potentially complicating effects of taxes and transaction costs unique to this market by using data from the foreign exchange market we are able to eliminate the tax effect and reduce the impact of transaction costs the question we address is whether the discrepancies observed in the treasury bill market are also observed in the foreign exchange market if they are then we have evidence that the differences are due to a combination of the cir effect and the transaction costs common to both markets if they are not then either the magnitude of the cir effect is much less in the foreign exchange market or the treasury bill results are due to the unique tax treatment and transaction costs of that market this paper is organized as follows in section i the trading mechanics of the forward and futures markets in foreign exchange are discussed section ii reviews the explanations for the discrepancies between the forward and futures prices for treasury bills the institutional differences between the foreign exchange and bill markets are also summarized to show which of these explanations cannot apply to the foreign exchange market in section iii the data are decribed and the empirical results are presented the conclusions are summarized in the final section

how relevant is volatility forecasting for financial risk management it depends if volatility fluctuates in a forecastable way volatility forecasts are useful for risk management hence the interest in volatility forecastability in the risk management literature volatility forecastability however varies with horizon and different horizons are relevant in different applications moreover existing assessments of volatility forecastability are plagued by the fact that they are joint assessments of volatility forecastability and an assumed model and the results can vary not only with the horizon but also with the assumed model to address this problem we develop a model free procedure for assessing volatility forecastability across horizons perhaps surprisingly we find that volatility forecastability decays quickly with horizon volatility forecastability although clearly of relevance for risk management at the short horizons relevant for say trading desk management may be much less important at longer horizons

mechanism design with weaker incentive compatibility constraints abstract we study an adverse selection problem where an agent is able to understate his productivity but not allowed to overstate it the solution to this problem is generally different than the solution to the standard problem where no restriction is made on the statements of the agent we identify a sufficient condition that does not depend on the distribution of types under which these two solutions coincide