buffer stocks and precautionary savings with loss aversion abstract this paper reexamines buffer stocks and precautionary savings in the presence of loss aversion we assume that agents are disappointment averse as in gul econometrica 59 1991 667 686 we show that the concavity of the marginal utility continues to determine precautionary saving but its effect is of a second order magnitude proportional to the square of the coefficient of variation compared to the first order effect proportional to the coefficient of variation induced by loss aversion we show that a stabilization fund that is rather small when agents are maximizing the conventional expected utility turns out to be rather large with loss aversion

reference dependent ambiguity abstract motivated by experimental and empirical evidence i study a framework where reference points such as a status quo endowment or default option can distort the way an individual responds to ambiguity i characterize a model of reference dependent maxmin expected utility and provide behavioral foundations for comparing reference dependent ambiguity attitudes i also illustrate some implications of reference dependent ambiguity for trade in an asset market including underdiversification no trade and the potential for a market collapse

crude oil corn ethanol nexus a contextual approach this paper offers a holistic study on the complex relationships between crude oil corn and ethanol during a turbulent period between 2006 and end of 2011 through a holistic mapping of the current market situation and a contextual analytical design we show that there exists a strong relationship between crude oil and corn markets on one side and crude oil and ethanol on the other however the price relationship between corn and ethanol was revealed to be less straightforward and is driven by the us government fuel policy furthermore the study indicates that corn markets have became more prone to volatility due to ethanol production especially when the demand for corn is high and or the crude oil prices are high enough to create a competitive market for ethanol

the knightian uncertainty and the risk premium and the risk free rate puzzles in japan and the u s abstract this paper proposes a new measure for knightian uncertainty under markovian economy and solves the risk premium and the risk free rate puzzle under knightian uncertainty in japan and the u s with plausible values for time preference and risk aversion parameters

optimism pessimism and financial bubbles this paper shows that it is possible to extend the scope of the existence of rational bubbles when uncertainty is introduced associated with rank dependent expected utility this rdu assumption can be viewed as a transformation of probabilities depending on the pessimism optimism of the agent the results show that pessimism favors the existence of deterministic bubbles when optimism may promote the existence of stochastic bubbles moreover under pessimism the rdu assumption may generate multiple bubbly equilibria the rdu assumption also leads to new conditions ensuring the absence of pareto optimality of the competitive equilibrium without bubbles these conditions still govern the existence of bubbles

the pricing effects of ambiguous private information when private information is observed by ambiguity averse investors asset prices may be informationally inefficient in rational expectations equilibrium this inefficiency implies lower asset prices as uninformed investors require a premium to hold assets and higher return volatility relative to informationally efficient benchmarks moreover asset returns are negatively skewed and may be leptokurtic inefficiency also leads to amplification in price of small changes in news relative to informationally efficient benchmarks public information affects the nature of unrevealed private information and the informational inefficiency of prices asset prices may be lower higher with good bad public information

optimal investment under ambiguous technology shocks abstract this paper analyzes the behavior of a firm facing an ambiguous technology shock and the effects of the attitude toward ambiguity on optimal capital investment using the smooth ambiguity model of klibanoff et al 2005 although it seems intuitive that an increase in ambiguity aversion always reduces the optimal capital investment this is not necessarily true because the shape of the production function plays a key role in determining the effect under some conditions we show that the optimal amount of capital investment increases decreases in ambiguity aversion if the production function is substitute complement and that this result is counterintuitive when the production function is substitute furthermore our main results hold if we assume the maxmin preferences in ghirardato et al 2004

uncertainty and risk in financial markets this paper considers a general equilibrium model in which the distinction between uncertainty and risk is formalized by assuming agents have incomplete preferences over statecontingent consumption bundles as in bewley 1986 without completeness individual decision making depends on a set of probability distributions over the state space a bundle is preferred to another if and only if it has larger expected utility for all probabilities in this set when preferences are complete this set is a singleton and the model reduces to standard expected utility in this setting we characterize pareto optima and equilibria and show that the presence of uncertainty generates robust indeterminacies in equilibrium prices and allocations for any specification of initial endowments we derive comparative statics results linking the degree of uncertainty with changes in equilibria despite the presence of robust indeterminacies we show that equilibrium prices and allocations vary continuously with underlying fundamentals equilibria in a standard risk economy are thus robust to adding small degrees of uncertainty finally we give conditions under which some assets are not traded due to uncertainty aversion

a note on the impact of options on stock return volatility abstract this paper measures the impact of option introductions on the return variance of underlying stocks past research generally finds a significant reduction in stock return variance following the listing of options through 1986 using a more extensive sample i compare changes in the return variance of optioned stocks to changes in the return variance of a control group since the average change in the control group is statistically indistinguishable from the average change in the optioned stocks i conclude that option introductions do not significantly affect stock return variance

asset allocation with distorted beliefs and transaction costs abstract in this paper we study the problem of the optimal portfolio selection with transaction costs for a decision maker who is faced with knightian uncertainty the decision maker s portfolio consists of one risky and one risk free asset and we assume that the transaction costs are proportional to the traded volume of the risky asset the attitude to uncertainty is modeled by the choquet expected utility we derive optimal strategies and bounds of the no transaction region for both optimistic and pessimistic decision makers the no transaction region of a pessimistic investor is narrower and its bounds lie closer to the origin than that of an optimistic trader moreover under the choquet expected utility the structure of the no transaction region is not necessarily a closed interval as it is under the standard expected utility model

precautionary principle and the optimal timing of environmental policy under ambiguity i consider a problem in environmental policy design in which i focus on stock pollutants in particular i consider stock pollutants that cause severe damage on the environment and do not depreciate at all once they are released into the atmosphere and the ocean the purposes of this paper are 1 to provide an economic foundation for environmental policies based on the precautionary principle and the 1992 rio declaration on environment and development and 2 to show that this optimal timing rule has a reservation property furthermore i analyze the effect of an increase in ambiguity on the optimal timing of adopting some environmental policy and show that an increase in ambiguity decreases the optimal timing of adopting the environmental policy

continuous and feasible implementation of rational expectations lindahl allocations abstract in this paper we consider bayesian implementation of rational expectations lindahl allocations for economic environments with public goods when agents are incompletely informed about environments we construct a continuous and feasible mechanism whose bayesian equilibrium allocations coincide with rational expectations lindahl allocations we not only allow the types of individuals to be unknown but also allow both the preferences and the initial endowments to be unknown to the designer in addition we allow some types of boundary equilibrium allocations and a continuous information structure journal of economic literatureclassification number c72 d71 d82 h41

horizon unbiased investment with ambiguity abstract in the presence of ambiguity about the driving force of market randomness we consider a dynamic portfolio choice problem without any predetermined investment horizon the investment criterion is formulated as a robust forward performance process reflecting an investor s dynamic preference adapted to the market evolution we show that the market risk premium and the utility risk premium jointly determine the investors trading direction and the worst case scenarios of the risky asset s mean return and volatility the closed form solution for the optimal investment strategies is given in the special settings of the constant relative risk aversion crra preference the resulting portfolio strategies highlight the effect of ambiguity on nonparticipation in the risky asset market from the forward performance point of view

the effect of ethanol listing on corn prices evidence from spot and futures markets abstract the use of corn for ethanol has been the topic of heated discussions in the media and among policy makers as part of this debate some observers have argued that the use of corn in the production of ethanol has had adverse effects on corn prices this paper contributes to this reviving debate by examining the impact of the listing of ethanol futures in the chicago board of trade on the spot and futures prices for corn we find a significant listing effect indicating that the listing of ethanol has had a positive contribution to both price and volatility in the corn market especially in the spot and the shorter maturity futures contracts and mostly through its interaction with trading volume in the corn market we discuss the policy implications of the findings for investors and its relevance for the ongoing debate on us energy policy we conclude with some suggestions for future research

incentive mechanism design for production economies with both private and public ownerships in this paper we dealwith the probl em of incentive mechanism design which yields efficient allocations for general mixed ownership economies when preferences individual endowments and coalition patterns among individuals are unknown to the planner we do so by doubly implementing the proportional solution for economies with any number of private sector and public sector commodities and any number of individuals as well as the coexistence of privately and publicly owned firms with general convex production possibility sets furthermore the mechanisms work not only for three or more agents but also for two agent economies journal of economic literature classification numbers c72 d61 d71 d82 2000 academic press

ambiguity optimism and pessimism in adverse selection models we investigate the effect of ambiguity and ambiguity attitude on the shape and properties of the optimal contract in an adverse selection model with a continuum of types using the parametric model of ambiguity and ambiguity aversion called the neo additive model chateauneuf eichberger and grant 2007 we show that it necessarily features efficiency and a jump at the top and pooling at the bottom of the distribution conditional on the degree of ambiguity the pooling section may or may not be supplemented by a separating section as a result ambiguity adversely affects the principal s ability to solve the adverse selection problem and therefore the least efficient types benefit from ambiguity with respect to risk conversely ambiguity is detrimental to the most efficient types this is confirmed in the comparative statics section

investment in new activities and the welfare cost of uncertainty abstract recent literature has shown that trade distortions are associated with first order costs stemming from the induced drop in the formation of new activities we demonstrate that uncertainty may induce similar welfare costs and that these costs apply also to a closed economy this argument is illustrated in romer s model of a dependent economy where foreign direct investment is needed to enable the importation of capital goods and intermediate products used in domestic production we show that knightian uncertainty inhibits the formation of new activities leading to first order losses whereas risk aversion alone leads to second order losses

ambiguity and uncertainty in ellsberg and shackle this paper argues that the similarities between ellsberg s and shackle s frameworks for discussing the limits of the probabilistic approach to decision theory are more important than usually admitted the paper discusses the grounds on which the ambiguity surrounding the decision maker in ellsberg s urn experiments can be deemed analogous to the uncertainty faced by shackle s entrepreneur taking crucial decisions the two authors insights are assessed and special attention is paid to the criteria for decision under uncertainty they put forward the paper establishes a link between ellsberg s and shackle s perspectives and the non additive probability approach of gilboa and schmeidler an approach that offers an alternative to standard probability calculus which can be of use to analyse both ambiguity and uncertainty the comparison between ellsberg and shackle draws on an interpretation of keynes s treatise on probability emphasising keynes s rejection of both well defined probability functions and maximisation as a guide to human conduct it is shown that keynes s viewpoint implies a reconsideration of the boundaries of probability theory that is in the same vein of ellsberg s and shackle s concern in the years of the consolidation of savage s new probabilistic mainstream copyright the author 2009 published by oxford university press on behalf of the cambridge political economy society all rights reserved oxford university press

interim efficient allocations under uncertainty abstract this paper considers an exchange economy under uncertainty with asymmetric information uncertainty is represented by multiple priors and posteriors of agents who have either bewley s incomplete preferences or gilboa schmeidler s maximin expected utility preferences the main results characterize interim efficient allocations under uncertainty that is they provide conditions on the sets of posteriors thus implicitly on the way how agents update the sets of priors for non existence of a trade which makes all agents better off at any realization of private information for agents with the incomplete preferences the condition is necessary and sufficient but for agents with the maximin expected utility preferences the condition is sufficient only a couple of necessary conditions for the latter case are provided

biofuel related price transmission literature a review abstract in this article an extensive review of the rapidly growing biofuel related time series literature is carried out the data used the modeling techniques and the main findings of this literature are discussed providing a review of this flourishing research area is relevant as a guidepost for future research this literature concludes that energy prices drive long run agricultural price levels and that instability in energy markets is transferred to food markets

ratio lindahl equilibria and an informationally efficient and implementable mixed ownership system abstract in this paper we formalize an informationally efficient and implementable mixed ownership economic institutional framework by using the ratio lindahl equilibrium that yields pareto efficient and individually rational allocations for public goods economies with general variable returns we consider the incentive aspects of the system by giving an incentive compatible informationally efficient and privacy preserving mechanism whose nash allocations coincide with ratio lindahl allocations moreover the mechanism is well behaved in the sense that it uses an individually feasible balanced and continuous outcome function and further has a message space of minimal dimension

the interaction between food prices and oil prices this paper provides a statistical methodology to estimate the impact of oil price uncertainty on food prices in doing so it examines the joint impact of oil price and food price uncertainties and their correlation on the food price also the theoretical model was applied to the oil based trinidad and tobago and the empirical results confirm the theoretical predictions the empirical results indicate that a higher oil price increases food price also a higher oil price volatility yields a higher food price moreover an increase in the oil supply reduces the food price

feasible and continuous implementation there has been a great deal of research in recent years investigating the question of whether or not there exist institutions game forms for which the set of equilibria will coincide with the set of walrasian equilibria in this paper we show the existence of a game form that is feasible both for equilibrium and disequilibrium strategies continuous and for which the set of nash equilibria coincides with the set of constrained walrasian equilibria for all pure exchange economies the game form allows agents to behave strategically both with respect to their preferences and their initial endowments

paralyzed by fear rigid and discrete pricing under demand uncertainty we propose a new theory of price rigidity based on firms knightian uncertainty about their competitive environment this uncertainty has two key implications first firms learn about the shape of their demand function from past observations of quantities sold this learning gives rise to kinks in the expected profit function at previously observed prices making those prices both sticky and more likely to reoccur second uncertainty about the relationship between aggregate and industry level inflation generates nominal rigidity we prove the main insights analytically and quantify the effects of our mechanism our estimated quantitative model is consistent with a wide range of micro level pricing facts that are typically challenging to match jointly it also implies significantly more persistent monetary non neutrality than in standard models allowing it to generate large real effects from nominal shocks

optimal pricing and quality choice of a monopolist under knightian uncertainty abstract this paper analyzes a simple vertical product differentiation model with demand uncertainty and derives a risk neutral monopolist s optimal market entry timing her optimal pricing and optimal quality choice by incorporating knightian uncertainty irreversibility and flexibility in quality enhancing investment into a continuous time stochastic model it is shown that an increase in knightian uncertainty induces decreases in the optimal price the optimal quality and the value of undertaking the quality enhancing investment by the monopolist the social optimal entry timing pricing and quality are also analyzed

on booms that never bust ambiguity in experimental asset markets with bubbles we study the effect of ambiguity on the formation of bubbles and on the occurrence of crashes in experimental asset markets a la smith suchanek and williams 1988 we extend their framework to an environment where the fundamental value of the asset is ambiguous we show that when the fundamental value is ambiguous asset prices tend to be lower than when it is risky although bubbles form in both the ambiguous and the risky environments additionally bubbles do not crash in the ambiguous case whereas they do so in the risky one these findings regarding depressed prices and the absence of crashes in the presence of ambiguity are in line with recent theoretical work stressing the crucial role of ambiguity to account for surprisingly low equity prices high returns as well as herding in asset markets

innovations in financial services relationships and risk sharing relationships between intermediaries and their customers have become increasingly important in recent years this paper argues that the need for costly ex ante information acquisition and analysis is a major barrier to the participation of investors and firms in sophisticated markets long term relationships between intermediaries and their customers in which intermediaries provide implicit insurance to customers can be an effective substitute for costly ex ante investigation in this way intermediaries allow firms and investors to reap the benefits of financial markets relationships are easiest to sustain when the ongoing benefits to both parties are high as a result competition may lower the benefits that can be obtained from relationships

iq and stock market participation stock market participation is monotonically related to iq controlling for wealth income age and other demographic and occupational information the high correlation between iq and participation exists even among the affluent supplemental data from siblings studied with an instrumental variables approach and regressions that control for family effects demonstrate that iq s influence on participation extends to females and does not arise from omitted familial and nonfamilial variables high iq investors are more likely to hold mutual funds and larger numbers of stocks experience lower risk and earn higher sharpe ratios we discuss implications for policy and finance research

model misspecification and underdiversification in this paper we study intertemporal portfolio choice when an investor accounts explicitly for model misspecification we develop a framework that allows for ambiguity about not just the joint distribution of returns for all stocks in the portfolio but also for different levels of ambiguity for the marginal distribution of returns for any subset of these stocks we find that when the overall ambiguity about the joint distribution of returns is high then small differences in ambiguity for the marginal return distribution will result in a portfolio that is significantly underdiversified relative to the standard mean variance portfolio

clarifying frank knight s discussion of the meaning of risk and uncertainty frank knight s 1921 famous distinction between risk and uncertainty has entered the jargon of economics and decision theory yet it appears to have gone unnoticed that his formulation suffers from an elementary confusion this note locates the source of the problem and proposes a reformulation that avoids it it is safe to say that frank knight 1921 is more widely quoted than read on his epony mous distinction between risk and uncertainty this of course is a fate that befalls many authorities and at least in the present case is probably not particularly serious for the knightian distinction has acquired a currency of its own that is both reasonably unambiguous and relatively widely understood certainly the convention of using the term risk to describe decision situations in which probabilities are available to guide choice and uncertainty to describe decision situations in which information is too imprecise to be summarised by probabilities is deeply ingrained in both economic theory and decision theory 1 that said and as those who are familiar with it will know the long disquisition on the meaning of risk and uncertainty that appears in chapter 7 of knight s risk uncertainty and profit is well worth reading 2 not only is his categorisation of different kinds of probability situation a good deal more subtle than the simple risk uncertainty dichotomy might imply he also has many interesting things to say about induction social laws the metaphysics of chance and the psychology of decision making under uncertainty in view of the many positive aspects of knight s discussion then not to mention how often it continues to be invoked it is particularly unfortunate that it turns out to suffer from an elementary confusion the purpose of what follows is to locate the source of this confusion and to propose a reformulation of knight s position that avoids it the hope is that readers may then be able to benefit from the many insights in knight s discussion

a unique informationally efficient allocation mechanism in economies with consumption externalities this article investigates the informational requirements of resource allocation processes in pure exchange economies with consumption externalities it is shown that the distributive lindahl mechanism has a minimal informational size of the message space and thus it is informationally the most efficient allocation process that is informationally decentralized and realizes pareto efficient allocations over the class of economies that include nonmalevolent economies furthermore it is shown that the distributive lindahl mechanism is the unique informationally efficient decentralized mechanism that realizes pareto efficient and individually rational allocations over a certain class of nonmalevolent economies

lindahl mechanisms and free riders several authors have proposed mechanisms whose nash equilibria yield lindahl tax allocations however as is well known so does the lindahl procedure with an auctioneer moreover the game forms of all these mechanisms and of any as yet undiscovered such mechanism all have the same normal form as does the lindahl procedure without an auctioneer the manipulative nash equilibria are consequently the same for all these mechanisms so that all have the traditional free rider problem and all have the same outcome under strategic behavior

asymmetric adjustments in the ethanol and grains markets this paper examines the long and short run asymmetric adjustments and pairs trades for nine pairs of spot and futures prices itemized as three own pairs for three different bio fuel ethanol types three own pairs for three related agricultural products namely corn soybeans and sugar and three cross pairs that included hybrids of the spot price of each of the agricultural products and an ethanol futures price most of the spreads asymmetric adjustments generally occur during narrowing the three ethanol pairs that contain the ecbot futures with each of chicago spot new york harbor spot and western european rotterdam spot show different long run adjustments arbitrage profitable opportunities and price risk hedging capabilities the asymmetric spread adjustments for the three grains are also different with corn spread showing the strongest long run widening adjustment and sugar showing the weakest narrowing adjustment among others the empirical analysis indicates the importance of potentially hedging the spot prices of agricultural commodities with ethanol futures contracts which sends an important message that the ethanol futures market is capable of hedging price risk in agricultural commodity markets the short run asymmetric adjustments for individual prices in the nine pairs with the exception of the corn own pair underscore the importance of futures prices in the price discovery and hedging potential particularly for ethanol futures

ambiguity models and the machina paradoxes daniel ellsberg 1961 constructed counterexamples to show the limitations of leonard j savage s 1954 subjective expected utility seu ellsberg s examples involved a comparison between objective uncertainty risk in which probabilities are known and subjective uncertainty in which they are not the prevailing prefer ence for objective over subjective uncertainty known as ambiguity aversion raised an important paradox for economic theory since ellsberg s classical work many models have been developed to generalize seu in order to accommodate the pref erence for objective over subjective uncertainty in the same manner as ellsberg mark j machina 2009 proposed two examples that falsify one of the seu generalizations david schmeidler s 1989 choquet expected utility ceu this article shows that the impact of machina s examples is not restricted to the model initially targeted his examples pose difficulties not only for ceu but also for the four other most popular and widely used models of ambiguity averse preferences namely maxmin expected utility itzhak gilboa and schmeidler 1989 variational preferences fabio maccheroni massimo marinacci and aldo rustichini 2006 a maxmin paolo ghirardato maccheroni and marinacci 2004 and the smooth model of ambiguity aversion peter klibanoff marinacci and sujoy mukerji 2005 consequently the implications for economics are more pro found than initially thought we also discuss marciano siniscalchi s 2009 vector expected utility veu model which can account for the typical ambiguity averse preferences in machina s examples finally we examine how our results are related to the uncertainty aver sion axiom which is assumed in virtually all commonly used decision models under ambiguity in particular we argue that machina s examples demonstrate that the uncertainty aversion axiom can be overly restrictive in some circumstances the article proceeds as follows section i presents the four models of ambiguity averse preferences which are alternatives to ceu and which are examined in this paper in section ii and iii the implications of machina s examples for these models are presented section iv discusses alternative models and the uncertainty aversion axiom

implementation of lindahl allocations with nontotal nontransitive preferences abstract the purpose of this paper is to present a mechanism the nash allocations of which coincide with the lindahl allocations even when preferences are nontransitive or nontotal this extension to include nontotal nontransitive preferences is potentially very important since preferences of agents are nontransitive nontotal in many cases in particular in the case where the players are groups of individuals besides the mechanism presented here uses outcome functions that are individually feasible balanced not merely weakly balanced continuous differentiable around nash equilibria and furthermore almost everywhere differentiable moreover the mechanism has a message space of minimal dimension

ambiguity aversion and incompleteness of contractual form subjective uncertainty is characterized by ambiguity if the decision maker has an imprecise knowledge of the probabilities of payoff relevant events in such an instance the decision maker s beliefs are better represented by a set of probability functions than by a unique probability function an ambiguity averse decision maker adjusts his choice on the side of caution in response to his imprecise knowledge of the odds the non additive expected utility model allows a formal characterization of such behaviour using this model this paper shows that ambiguity aversion can explain the existence of incomplete contracts the setting for the demonstration is the investment hold up model which has been the focus of much of the recent research on the implications of incomplete contracts

implementation of balanced linear cost share equilibrium solution in nash and strong nash equilibria abstract this paper considers the incentive aspect of the balanced linear cost share equilibrium blcse which yields an endogenous theory of profit distribution for public goods economies with convex production technologies we do so by presenting an incentive compatible mechanism which doubly implements the blcse solution in nash and strong nash equilibria so that nash allocations and strong nash allocations coincide with blcse allocations the mechanism presented here allows not only preferences and initial endowments but also coalition patterns to be privately observed in addition it works not only for three or more agents but also for two agent economies

on the existence of optimal truth dominant mechanisms abstract the existence of optimal dominant strategy mechanisms has been shown only for quadratic valuation functions this paper shows that non trivial pareto efficient and truth dominant mechanisms exist for a slightly larger set of valuation functions

biofuels and food security the biofuel market created the linkage between energy and agricultural market prices biofuel policies and energy prices set the floor price of feedstock prices and the energy prices and the upper limit of the biofuel blend ratio can decide the ceiling of feedstock prices on the other hand biofuels can also transmit price volatility from energy to agricultural markets despite not always being the cause of price volatility of feedstock and related agricultural commodity prices brazilian bioethanol can play a crucial role in stabilizing the sugar market one of the most crucial problems for increasing biofuel production is the competition with food and food related demand and agricultural resources the definition of competition between biofuels and food can be divided into two dimensions the competition with food and food related demand and the competition with the agricultural resources the feedstock of the second generation biofuels can compete with food and food related demand and agricultural resources the development of second generation biofuels may not solve the problems associated with the competition between biofuels and food however the competition between biofuels and food doesn t always have a negative impact on food security the competition and food security impact on different dimensions biofuels can contribute to agricultural and rural development and can have a positive impact on a national and sub national level but they can also have a negative impact on household levels in the same country international action is required to monitor whether biofuels can have a negative impact on food security and nutrition security at national sub national and household levels biofuels should be compatible with and must not threaten food security the fao in collaboration with other international organizations will have the responsibility of monitoring the impact of biofuels on food security and proposing policy recommendations to individual countries based on the results of the monitoring

implementation in economies with non convex production technologies unknown to the designer this paper deals with the problem of incentive mechanism design in non convex production economies when production sets and preferences both are unknown to the designer we consider nash implementation of loss free average cost marginal cost voluntary trading and quantity taking pricing equilibrium allocations in economies involving increasing returns to scale or more general types of non convexities the mechanisms presented in the paper are well behaved they are feasible continuous and use finite dimensional message spaces moreover the mechanisms work not only for three or more agents but also for two agent economies

food versus fuel what do prices tell us abstract sorting out the impacts of biofuels on global agricultural commodity prices is impossible without turning to data and distinguishing between the short run versus the long run impacts using time series prices on fuels and agricultural commodities the aim is to investigate the long run cointegration of these prices simultaneously with their multivariate short run interactions results indicate no direct long run price relations between fuel and agricultural commodity prices and limited if any direct short run relationships in terms of short run price movements sugar prices are influencing all the other agricultural commodity prices except rice with sugar the number one world input for ethanol results indicate increased ethanol production is potentially influencing short run agricultural commodity prices overall results support the effect of agricultural commodity prices as market signals which restore commodity markets to their equilibria after a demand or supply event shock

opaque trading disclosure and asset prices implications for hedge fund regulation we construct a rational expectations equilibrium model to investigate the effect of ambiguity about hedge fund strategies on market efficiency and aggregate welfare in our model some traders mutual funds view the equilibrium trading strategies of other traders hedge funds as ambiguous this ambiguity limits the ability of mutual funds to infer information from prices and affects the market performance we use this analysis to investigate the implications of regulations that affect the amount of ambiguity about hedge fund strategies or the cost of operating a hedge fund our analysis demonstrates how regulations affect asset prices and welfare through their influence on opaque trading

incomplete preferences and equilibrium in contingent markets this paper shows that betting or speculative trading between agents with incomplete preferences is likely to occur if agents have access to convex choice sets this contrasts sharply with endowment economy models where preference incompleteness often hinders betting speculative trading or mutually beneficial insurance arrangements our results imply that decision makers with identical tastes and identical feasible sets will potentially gain from speculative trade for generic status quo allocations we also develop a framework for endogenizing the status quo allocations of decision makers that are treated exogenously in the existing literature finally we provide a tractable differential representation of status quo allocations equilibria and conditions where speculative trade may or may not emerge

pension plan funding technology choice and the equity risk premium in this paper the impact of lazear contracts with defined benefit pensions on aggregate technology composition and the aggregate risk premium is examined in the presence of capital market constraints affecting workers defined benefit pensions bias the economy towards risk free production leveraging the risky technology relaxes the constraints and results in more risky production and a fall in the aggregate risk premium this effect holds with risky debt and low pension shortfall risk but breaks down with high pension shortfall risk a key prediction is that as lazear contracts become less common risky production will increase and the aggregate risk premium will fall

savage in the market we develop a behavioral axiomatic characterization of subjective expected utility seu under risk aversion given is an individual agent s behavior in the market assume a finite collection of asset purchases with corresponding prices we show that such behavior satisfies a revealed preference axiom if and only if there exists a seu model a subjective probability over states and a concave utility function over money that accounts for the given asset purchases

status quo bias multiple priors and uncertainty aversion motivated by the extensive evidence about the relevance of status quo bias both in experiments and in real markets we study this phenomenon from a decision theoretic prospective focusing on the case of preferences under uncertainty we develop an axiomatic framework that takes as a primitive the preferences of an agent for each possible status quo option and provide a characterization according to which the agent considers a full dimensional set of possible priors and abandons her status quo option only if she finds an alternative that returns a higher expected utility for each of these priors we then show that in this framework the very presence of a status quo induces the agent to be more uncertainty averse than she would be without a status quo option

food scares in an uncertain world we develop a model that explains the stylized facts of food scares an immediate and sharp decline in consumption of the product followed by a slow and frequently partial recovery of demand after the scare passes the model is used in conjunction with the natural experiment afforded by the mad cow crisis to elicit empirical information on decision makers perception of uncertainty our theoretical and quantitative results suggest that observed behavior is consistent with sharp changes in beliefs and the presence of knightian uncertainty as measured by the degree of imprecision in our model

keynes meets markowitz the trade off between familiarity and diversification we develop a model of portfolio choice to nest the views of keynes who advocates concentration in a few familiar assets and markowitz who advocates diversification we use the concepts of ambiguity and ambiguity aversion to formalize the idea of an investor s familiarity toward assets the model shows that for any given level of expected returns the optimal portfolio depends on two quantities relative ambiguity across assets and the standard deviation of the expected return estimate for each asset if both quantities are low then the optimal portfolio consists of a mix of familiar and unfamiliar assets moreover an increase in correlation between assets causes an investor to increase concentration in familiar assets flight to familiarity alternatively if both quantities are high then the optimal portfolio contains only the familiar asset s as keynes would have advocated in the extreme case in which both quantities are very high no risky asset is held nonparticipation this paper was accepted by brad barber teck ho and terrance odean special issue editors

the impact of the listing of options in the foreign exchange market abstract this paper documents the impact of the introduction of foreign currency options and options on foreign currency futures on the underlying securities we find that the volatility of exchange rates decreases following the listing of options for a majority of the currencies under consideration in addition we find that trading volume and open interest in currency futures increases after option introduction this evidence is consistent with the notion that derivative securities are important innovations for stabilizing and increasing liquidity in the market for the underlying assets

cattle as a consistently resilient agricultural commodity this study compares a range of agricultural commodities over periods of varying economic circumstances these commodities are examined over three categories including returns risk and contributi

implementation of the lindahl correspondence by a single valued feasible and continuous mechanism this paper considers the problem of designing mechanisms whose nash allocations coincide with the lindahl allocations for public goods economies with more than one private good unlike previous mechanisms the mechanism presented here has a single valued feasible and continuous outcome function furthermore when there are no public goods in economies feasible and continuous implementation of the constrained walrasian correspondence can be obtained as a corollary of our theorem 1

the impact of energy derivatives on the crude oil market we examine the effects of energy derivatives trading on the crude oil market there is a common public and regulatory perception that derivative securities increase volatility and can have a destabilizing effect on the underlying market consistent with this view we find an abnormal increase in volatility for three consecutive weeks following the introduction of nymex crude oil futures while there is also evidence of a longer term volatility increase this is likely due to exogenous factors such as the continuing deregulation of the energy markets subsequent introductions of crude oil options and derivatives on other energy commodities have no effect on crude oil volatility we also examine the effects of derivatives trading on the depth and liquidity of the crude oil market this analysis reveals a strong inverse relation between the open interest in crude oil futures and spot market volatility specifically when open interest is greater the volatility shock associated with a given unexpected increase in volume is much smaller

addressing uncertainty in economics and the economy this article explores the way society in general and economists in particular deal with fundamental uncertainty it is argued that uncertainty is interdependent with the evolution of institutions and behaviour including that designed to help society cope with uncertainty whilst some mainstream theory does address uncertainty it employs a much narrower concept than fundamental uncertainty generally in spite of the evident increase in fundamental uncertainty during the crisis most mainstream theory ignores it although ignoring uncertainty can sometimes be a successful coping mechanism it is argued that as a blanket coping mechanism ignoring uncertainty seriously limits the realism of theory and therefore also practice and policy it is concluded that economists should embrace uncertainty by tailoring methodologies and theories to address it this would provide a more fruitful basis for policy aimed at reducing uncertainty in the economy and also reducing our own uncertainty

the market for sweepstakes this paper studies the market for monopolistically supplied sweepstakes we derive equilibrium demands for fixed prize and variable prize sweepstakes and determine the profit maximizing prize level and pay out ratio respectively it can be profitable to offer each type of sweepstake when there is a large enough number of weighted utility consumers who have constant absolute risk attitudes are strictly averse to small as well as symmetric risks and display longshot preference behaviour moreover for the variable prize sweepstake the supplier will generally find it profitable to combine sweepstakes targeting two smaller populations and offer a single sweepstake to the combined population this implication is corroborated by the recent spate of mergers of smaller state lotteries into larger ones

ambiguity attitudes in a large representative sample using a theorem showing that matching probabilities of ambiguous events can capture ambiguity attitudes we introduce a tractable method for measuring ambiguity attitudes and apply it in a large representative sample in addition to ambiguity aversion we confirm an ambiguity component recently found in laboratory studies a insensitivity the tendency to treat subjective likelihoods as 50 50 thus overweighting extreme events our ambiguity measurements are associated with real economic decisions specifically a insensitivity is negatively related to stock market participation ambiguity aversion is also negatively related to stock market participation but only for subjects who perceive stock returns as highly ambiguous this paper was accepted by james smith decision analysis

uncertainty aversion in a heterogeneous agent model of foreign exchange rate formation this paper provides what we believe to be the first empirical test of whether investors in the foreign exchange market are uncertainty averse we do this using a heterogeneous agents model in which fundamentalist and chartist beliefs of the exchange rate co exist and are allowed to be either uncertainty neutral or uncertainty averse uncertainty aversion is modelled using the maxmin expected utility approach we find significant evidence of uncertainty aversion in the fx market where in particular fundamentalists are found to be largely uncertainty neutral while chartists are mainly uncertainty averse inclusion of uncertainty averse agents significantly improves the performance of the model

applying regret theory to investment choices currency hedging decisions we apply regret theory an axiomatic behavioral theory to derive closed form solutions to optimal currency hedging choices investors experience regret of not having chosen the ex post optimal hedging decision hence investors anticipate their future experience of regret and incorporate it in their objective function we derive a model of financial decision making with two components of risk traditional risk volatility and regret risk we find results that are in sharp contrast with traditional expected utility loss aversion or disappointment aversion theories we discuss the empirical implications of our model and its ability to explain observed hedging behavior

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

decision theory under ambiguity we review recent advances in the field of decision making under uncertainty or ambiguity we start with a presentation of the general approach to a decision problem under uncertainty as well as the standard bayesian treatment and issues with this treatment we present more general approaches choquet expected utility maximin expected utility smooth ambiguity and so forth that have been developed in the literature under the name of models of ambiguity sensitive preferences we draw a distinction between fully subjective models and models incorporating explicitly some information we review definitions and characterizations of ambiguity aversion in these models we mention the challenges posed by some of the models presented we end with a review of part of the experimental literature and applications of these models to economic settings

risk versus ambiguity and international security design abstract we study portfolio allocation and characterize contracts issued by firms in the international financial market when investors exhibit ambiguity aversion and perceive ambiguity in assets issued in foreign locations increases in the variance of their risky production process cause firms to issue assets with a higher variable payment equity hikes in investors perceived ambiguity have the opposite effect and lead to less risk sharing entrepreneurs from capital scarce countries finance themselves relatively more through debt than equity they are thus exposed to higher volatility per unit of consumption the expected returns on capital invested in capital scarce countries may also be lower such results do not hold in the absence of ambiguity that is when investors only perceive risk new facts uncovered from cross country firm level data are consistent with our model

rollover risk and market freezes the debt capacity of an asset is the maximum amount that can be borrowed using the asset as collateral we model a sudden collapse in the debt capacity of good collateral we assume short term debt that must be frequently rolled over a small transaction cost of selling collateral in the event of default and a small probability of meeting a buy to hold investor we then show that a small change in the asset s fundamental value can be associated with a catastrophic drop in the debt capacity the kind of market freeze observed during the crisis of 2007 to 2008 one of the many striking features of the crisis of 2007 to 2008 was the sudden freeze in the market for the rollover of short term debt from an in stitutional perspective the inability to borrow overnight against high quality but long term assets was a market failure that effectively led to the demise of a substantial part of investment banking in the united states more broadly it led to the collapse in the united states the united kingdom and other countries of banks and other financial institutions that had relied on signifi cant maturity mismatch between assets and liabilities and in particular on the rollover of short term wholesale debt in the asset backed commercial paper abcp and overnight sale and repurchase repo markets in this paper we are interested in developing a model of a sudden collapse in the ability to borrow short term against long lived assets in the absence of obvious problems of asymmetric information or fears about the value of col lateral we refer to this phenomenon as a market freeze more precisely a market freeze occurs when the debt capacity the maximum amount of collat eralized borrowing that can be supported by an asset is a small fraction of the fundamental value the economic value measured by the net present value npv of the stream of future returns an extreme form of a market freeze occurs when the fundamental value is close to the maximum possible value of the asset whereas the debt capacity is close to the minimum possible value of the asset

sequential two player games with ambiguity if players beliefs are strictly non additive the dempster shafer updating rule can be used to define beliefs off the equilibrium path we define an equilibrium concept in sequential two person games where players update their beliefs with the dempster shafer updating rule we show that in the limit as uncertainty tends to zero our equilibrium approximates bayesian nash equilibrium by imposing context dependent constraints on beliefs under uncertainty

endogenous discounting wariness and efficient capital taxation abstract when the discount factors that infinite lived consumers use at each date are not predetermined but are instead chosen within some set depending on what the consumption plan is impatience might not hold more precisely if the utility is the infimum of discounted utilities over that set of discount factor sequences then preferences may be just upper semi impatient such lack of lower semi impatience which we refer to as wariness consists in neglecting distant gains but not distant losses examples are the precautionary case a concern with the worst lifetime outcome and the habit persistence case a concern with a fall in living standards the implementation of efficient allocations by trading assets sequentially requires taxes that avoid excessive savings by raising the opportunity of cost of saving up to the point of matching the marginal benefit of dishoarding at distant dates taxes on equilibrium plans are zero in many contexts

portfolio choices and asset prices the comparative statics of ambiguity aversion we investigate the comparative statics of more ambiguity aversion as defined by klibanoff marinacci and mukerji 2005 in the context of the static two asset portfolio problem it is not true in general that more ambiguity aversion reduces the demand for the uncertain asset we exhibit some sufficient conditions to guarantee that ceteris paribus an increase in ambiguity aversion reduces the demand for the ambiguous asset and raises the equity premium for example this is the case when the set of plausible distributions of returns can be ranked according to the monotone likelihood ratio order we also show how ambiguity aversion distorts the price kernel in the alternative portfolio problem with complete markets for contingent claims

ambiguity and nonparticipation the role of regulation we investigate the implications of ambiguity aversion for performance and regulation of markets in our model agents decision making may incorporate both risk and ambiguity and we demonstrate that nonparticipation arises from the rational decision by some traders to avoid ambiguity in equilibrium these participation decisions affect the equilibrium risk premium and distort market performance when viewed from the perspective of traditional asset pricing models we demonstrate how regulation particularly regulation of unlikely events can moderate the effects of ambiguity thereby increasing participation and generating welfare gains our analysis demonstrates how legal systems affect participation in financial markets through their influence on ambiguity the author 2009 published by oxford university press on behalf of the society for financial studies all rights reserved for permissions please e mail journals permissions oxfordjournals org oxford university press

limited participation and consumption saving puzzles a simple explanation and the role of insurance in this paper we show that the existence of a large negative wealth shock and insufficient insurance against such a shock could explain both the limited stock market participation puzzle and the low consumption high savings puzzle we then conduct an empirical analysis on the relation between household portfolio choices and access to private insurance and various types of government safety nets the empirical results demonstrate that a lack of insurance against large negative wealth shocks is positively correlated with lower participation rates and higher saving rates overall the evidence suggests an important role of insurance in household investment and savings decisions

general equilibrium wariness and efficient bubbles abstract wary consumers overlook gains but not losses in remote sets of dates or states as preferences are upper but not lower mackey semi continuous bewley s 1972 4 result on existence of equilibrium whose prices are not necessarily countably additive holds wariness is related to lack of myopia and to ambiguity aversion and therefore to bewley s 1986 6 work on knightian uncertainty wary infinite lived agents have weaker transversality conditions allowing them to be creditors at infinity and for bubbles to occur in positive net supply assets completing the markets there are efficient allocations that can only be implemented with asset bubbles

microstructure and ambiguity a goal for stock exchanges is to increase participation by firms and investors we show how specific features of the microstructure can reduce perceived ambiguity and induce participation by both investors and issuers we develop a model with sophisticated traders who we view as expected utility maximizers with rational expectations and unsophisticated traders who we view as rational traders facing ambiguity about the payoffs to participating in the market we show how designing markets to reduce ambiguity can benefit investors through greater liquidity exchanges through greater volume and issuing firms through a lower cost of capital