Existence of a continuous utility function with path monotonicity: the Wold approach

Summary This paper uses the approach of Wold to prove the existence of a continuous utility function on a subset ofR ⁿ with a path monotonicity assumption. This result is then extended to a Banach space.The research for this paper was begun while visiting the University of Cambridge and the London School of Economics in 1988. I should like to thank Dr. A. Beardon, Professor M. Desai, Professor L. Foldes and Dr. A. Horsley for their hospitality. Also, I am grateful to an anonymous referee for comments that led to an improvement in the exposition.     

Subjective recursive expected utility

We axiomatize a subjective version of the recursive expected utility model. This development extends the seminal results of Kreps and Porteus (Econometrica 46:185–200 (1978)) to a subjective framework and provides foundations that are easy to relate to axioms familiar from timeless models of decision making under uncertainty. Our analysis also clarifies what is needed in going from a represention that applies within a single filtration to an across filtration representation.Part of this research was conducted when Ozdenoren visited MEDS in Fall 2003. We thank Tapas Kundu, Costis Skiadas, Jean-Marc Tallon and Tan Wang for helpful discussions and also thank audiences at Koc University, Northwestern University, the CERMSEM conference “ Mathematical Models in Decision Theory” at Universite Paris I, and the FUR XI conference on foundations and applications of utility, risk and decision theory     

Revealed preference and differentiable demand

Summary. We prove that, for finitely many demand observations, the Strong Axiom of Revealed Preference tests not only the existence of a strictly concave, strictly monotone and continuous utility generator, but also one that generates an infinitely differentiable demand function. Our results extend those of previous related results (Matzkin and Richter, 1991; Chiappori and Rochet, 1987), yielding differentiable demand functions but without requiring differentiable utility functions.Received: 1 November 2001, Revised: 5 February 2004, JEL Classification Numbers: D11, D12. Correspondence to: Kam-Chau WongThis is a much revised version of Lee and Wong (2001). We are grateful to the Referee for valuable suggestions. We also thank Professor Marcel K. Richter for his comments.     

Market clearing, utility functions, and securities prices

Summary. We prove the existence of equilibrium in a continuous-time finance model; our results include the case of dynamically incomplete markets as well as dynamically complete markets. In addition, we derive explicitly the stochastic process describing securities prices. The price process depends on the risk-aversion characteristics of the utility function, as well as on the presence of additional sources of wealth (including endowments and other securities). With a single stock, zero endowment in the terminal period, and Constant Relative Risk Aversion (CRRA) utility, the price process is geometric Brownian motion; in essentially any other situation, the price process is not a geometric Brownian motion.JEL Classification Numbers: D52.This paper is part of my Dissertation (UC Berkeley). I am very grateful to my advisor Professor Robert M. Anderson. I also would like to thank Steve Evans, Roger Purves, Jacob Sagi, Chris Shannon and the participants of the 2002 NBER General Equilibrium Conference at the University of Minnesota (Minneapolis) for very helpful discussions and comments. This work was supported by Grant SES-9710424 from the National Science Foundation.     

Non-cooperative games with a continuum of players whose payoffs depend on summary statistics

Summary. We consider static non-cooperative games with a continuum of small players whose payoffs depend on their own actions and finitely many summary statistics of the aggregate strategy profile. We prove the existence of an equilibrium in pure strategies without any convexity restrictions on payoffs or the common action space. We show that this result applies to a broad class of monopolistic competition models. Received: April 13, 2001; revised version: December 18, 2001 RID="*" ID="*" The result in this paper generalizes a result in my PhD dissertation supervised by M. Ali Khan and Joe Harrington. I thank them for support and encouragement. I also thank Sung Kim, Bruce Nanney, Ashvin Rajan, Kali Rath, and an anonymous referee for comments. The usual disclaimer applies.     

Market equilibrium with heterogeneous recursive-utility-maximizing agents

Summary This paper considers a heterogeneous agent Lucas style exchange economy. For a class of recursive utility functions containing the standard additive expected utility functions, I demonstrate that there exist market equilibria characterized by stationary (ergodic) Markov processes for consumption, portfolio holdings, asset prices and the unobserved utilities. No assumptions about market completeness are made, and there are no restrictions on the underlying information filtration.Other contributions of this paper include: (i) an existence and uniqueness theorem of intertemporal utility for the general class of recursive generators; (ii) the optimum principle as well as its corresponding Euler equation derived for the agent's consumption and portfolio choice problem under recursive utility, and (iii) a single-agent equilibrium asset pricing formula which generalizes that of Epstein and Zin (1989).This paper is a part of my PhD dissertation at the University of Toronto. I would like to thank Larry Epstein for his enthusiastic supervision, helpful discussion and valuable comments. Thanks also to Tan Wang and especially Darrell Duffie for valuable comments.     

Existence and specific characters of rentiers: a savers-spenders theory approach

Summary. Using the savers-spenders theory developed by Mankiw (2000, AER), we propose microfoundations to the existence of rentiers in macroeconomic growth models. From an OLG model which acknowledges the great heterogeneity of consumer behavior apparent in the data, we capture the dynamic considerations of potential rentiers as a natural consequence of intertemporal utility maximization and we analyze realistic characteristics (proportion, wealth, propensity to save) of rentiers.JEL Classification Numbers: E13, D64, J22.This paper is adapted from the fourth chapter of my Ph.D Thesis. Then, I thank Alain VENDITTI, my Ph.D Supervisor and Antoine dAUTUME and Pierre PESTIEAU my Ph.D Referees. Earlier version of this paper were presented at the International conference: New perspectives on (un)stability: the role of heterogeneity at Marseille, June 7-9, 2001 and at the X-th Spring School of the Associated European Laboratory (CNRS-FNRS/CORE-GREC-GREQAM) at Aix, 2001. I thank conference participants, in particular Olivier CHARLOT, Christian GHIGLINO, Kiminori MATSUYAMA and Philippe MICHEL for suggestions, helpful comments and discussions. I also thank a referee of this journal for his constructive comments.     

Mechanism design for general screening problems with moral hazard

Summary We study the problem faced by an incomplete information monopolist seeking to design a line of contracts so as to simultaneously screen consumers by type and resolve the moral hazard problems associated with contract performance. We formulate the monopolist's problem as a mechanism design problem in which the set of consumer types is taken to be a Polish space, and the contract space an arbitrary compact metric space. Allowing for risk aversion on the part of the monopolist and consumers, and taking as the feasible set of mechanisms the collection of all measurable functions defined on the space of consumer types with values in the space of contracts, we present a new characterization of incentive compatibility in an infinite dimensional setting which allows us to reformulate the monopolist's design problem as an unconstrained optimization problem (i.e., as a problem without the incentive compatibility contraints). Using simple techniques, we then demonstrate the existence of an optimal screening mechanism for the monopolist. We thus extend the existing analysis of the incomplete information monopoly problem to an infinite dimensional setting with moral hazard, and we provide an existence result not available in the existing literature.I thank seminar participants at Indiana University, McGill University, and the University of Calgary for helpful comments. I also thank Kerry Back, Bob Becker, Praveen Kumar, Mark Johnson, Ramon Marimon, Murat Sertel, Bill Sealey, Gordon Sick, and Nicholas Yannelis for helpful comments. The comments and suggestions of an anonymous referee are especially appreciated. I am solely responsible for any errors.     

Existence of optimal strategies in linear multisector models

In this paper, we give a sufficient and almost necessary condition for the existence of optimal strategies in linear multisector models when time is continuous, consumption is limited to one commodity, the instantaneous utility is of the CES type, and available technology allows a positive growth rate.JEL Classification Numbers: C62, O41 We thank an anonymous referee of this journal for careful scrutiny and very useful suggestions     

Cournot-Walras and Cournot equilibria in mixed markets: A comparison

Summary In this paper, we show that, in markets with a continuum of traders and atoms, the set of Cournot-Walras equilibria and the set of Cournot equilibria may be disjoint. We show also that, when the preferences of the traders are represented by Cobb-Douglas utility functions, the set of Cournot-Walras equilibria and the set of Cournot equilibria have a nonempty intersection.I would like to thank R. Amir, B. de Meyer, J. J. Gabszewicz, J.-F. Mertens, H. Polemarchakis and L. Ventura for some helpful discussions about the questions examined in the present work.     

Existence,uniqueness, and stability of equilibrium in an OLG economy

Summary. This paper presents sufficient conditions for the existence of a unique and globally stable steady state equilibrium for OLG economies with production. The conditions impose separate requirements on the utility and production functions. Moreover, the conditions do not require assumptions concerning the third order derivatives of the production and utility functions.Received: 12 August 2002, Revised: 7 January 2003, JEL Classification Numbers: D50, D91, E13, O41.I would like to thank Nick Baigent, Laurie Conway, Karl Farmer, Christian Gehrke, and Hideo Konishi for helpful comments. I am grateful to an anonymous referee for his or her comments.     

A contribution to duality theory,applied to the measurement of risk aversion

This paper determines the precise connection between the curvature properties of an objective function and the ray-curvature properties of its dual. When the objective function is interpreted as a Bernoulli or cardinal utility function, our results characterize the relationship between an agent’s attitude towards income risks and her attitude towards risks in the underlying consumption space. We obtain these results by developing and applying a number of representation theorems for concave functions.The work of Juan E. Martínez-Legaz has been supported by the Spanish Ministry of Science and Technology and the FEDER, project BEC2002-00642, and by the Departament d’Universitats, Recerca i Societat de la Informació, Direcció General de Recerca de la Generalitat de Catalunya, project 2001SGR-00162. He also thanks the Barcelona Economics Program of CREA for its support. John Quah would like to acknowledge with gratitude the financial support of the ESRC (grant number R000271171). He would also like to thank the Department of Economics at UC Berkeley, whose hospitality he enjoyed while completing this project. Both authors would like to thank Simon Cowan for pointing the way to some important references. They are also very grateful to the referee whose insightful suggestions led to a much improved paper     

Fertility,human capital and the wealth of families

Summary An overlapping generations model with parental altruism is examined. The existence of the optimal value function in a model with an endogenous discount rate is proven. Two development regimes are produced: a high fertility, low income and no growth steady state, and a perpetual growth equilibrium with low fertility and rising income.This paper is adapted from my dissertation. I would like to thank the members of my dissertation committee for helpful comments and suggestions, Messrs, Gary S. Becker, Robert E. Lucas, Jr., Kevin M. Murphy and Sherwin Rosen. I'd like to thank Brooks Pierce, Paul Romer, Ken Judd, Beth Ingram, Ed Prescott and Fernando Alvarez. I also thank the workshop participants of the University of Chicago, University of Pennsylvania, University of Toronto, University of Rochester, University of Washington, Penn State University, University at Buffalo, SUNY, Columbia University and University of Iowa.     

Is Kreps-Porteus utility distinguishable from intertemporal expected utility?

Summary In a Lucas (1978) model, with a Kreps-Porteus (1978) nonexpected utility, the following property of equilibrium holds generically in the space of finite-state, Markov output growth rate processes: equilibrium price of equity is distinct from that implied by any intertemporally additive expected utility satisfying specified regularity conditions. In that sense the more general utility functions are observationally distinguishable from the standard expected utility specification.I would like to thank Larry G. Epstein for posing to me the problem studied in this paper and for many suggestions and comments. I am also grateful to Darrell Duffie for helpful suggestions. I am responsible for errors. This papers is part of my Ph.D. thesis at University of Toronto.     

Multi-lender coalitions in costly state verification models

The paper analyzes the endogenous formation of a financial intermediary, modelled as a multi-lender coalition, as the trade-off between economies of scale in monitoring and a ‘cost’ associated with the partial loss of control over the investments the multi-lender coalition makes. In contrast with previous contributions (e.g., Williamson in J Monet Econ 18:159–179, 1986), the model can account for the coexistence of financial intermediation and direct lending (a non-trivial equilibrium). We prove the existence of such non-trivial equilibria and provide a complete characterization of them. In particular, the stronger the diversity of opinions, the smaller the coalition size is. I owe Pierpaolo Battigalli and Larry Samuelson a special debt for their insightful comments and encouragements. I am also grateful to the co-editor, Stephen Williamson, and an anonymous referee for insightful comments. I also like to thank Rabah Amir, Francis Bloch, Guillaume Carlier, Pascal Courty, Martin Hellwig, Bart Lipman, Jean-Marc Tallon and Anne Villamil for helpful discussions. Finally, I thank the THEMA, University Cergy-Pontoise, where part of this paper was written, for their hospitality.     

Option exercise with temptation

This paper adopts the Gul and Pensendorfer self-control utility model to analyze an agent’s option exercise decision under uncertainty over an infinite horizon. The agent decides whether and when to do an irreversible activity. He is tempted by immediate gratification and suffers from self-control problems. The cost of self-control lowers the benefit from continuation or stopping and may erode the option value of waiting. When applied to the investment and exit problems, the model can generate the behavior of procrastination and preproperation. In addition, unlike the hyperbolic discounting model, the model here provides a unique prediction. I thank Drew Fudenberg, Bart Lipman, Neng Wang, and participants in the BU theory lunch workshop and in the Canadian Economic Theory Conference 2005 for helpful discussions. I am especially grateful for valuable suggestions from an anonymous referee and coeditor Steve Williamson. The BU ISP Seed Grant has supported this research.     

Expected utility inequalities: theory and applications

Suppose we know the utility function of a risk averse decision maker who values a risky prospect X at a price CE. Based on this information alone I develop upper bounds for the tails of the probabilistic belief about X of the decision maker. In the paper I also illustrate how to use these expected utility bounds in a variety of applications, which include the estimation of risk measures from observed data, option valuation, and the study of credit risk. I would like to thank John Cochrane, Tom Cosimano, Amanda Friedenberg, George Korniotis, Markus Brunermeier and Paul Schultz for helpful discussions and to participants at two Notre Dame seminars, at the 2006 Spring Midwest Economic Theory and International Economics Conference, and at the 2006 Australasian Meeting of the Econometric Society for their very useful comments. I began working on this project during a year-long visit to the Central Bank of Venezuela. I gratefully acknowledge their hospitality and financial support.     

Bayesian estimation of duration models: An application of the multiperiod probit model

The multiperiod probit model is presented and Bayesian estimation using the Gibbs sampler with data augmentation is described. As an empirical illustration, the multiperiod probit model is then used to estimate a duration model using employment duration data for the Canadian province of New Brunswick. Bayesian estimation with unobserved heterogeneity is shown to be a simple extension of estimation of a duration model with no unobserved heterogeneity. More importantly, perhaps, some numerical problems encountered by other authors using Maximum Likelihood are avoided.I would like to thank M. Baker, G. Koop, A. Melino and D. Poirier for helpful comments and discussions. I would also like to thank M. Baker for providing his data.     

Non-stationary,stable Markov processes on a continuous state space

We extend our previous result on simple stable Markov (SSM) processes to the case where the state space is continuous. As anapplication we show the existence of a competitive general equilibrium of a cobweb model where price volatility is generated both by exogenous shocks and by stochastic, so called generating variables (that may be interpreted as sunspots) that govern the correlation of the rational beliefs of individual agents. I would like to thank Danish Social Science Foundation, The Carlsberg Foundation, Stanford Institute for Theoretical Economics (SITE) and Universita Cattolica for financial help. I would also like to thank Trinidad Casasus, Mordecai Kurz, an anonymous referee as well as participants at SITE, ESAM (2004) and ESEM (2004) for helpful discussions and comments. Peter Harremoes provided me with an illuminating counter example and Hiro Nakata provided many comments that helped improve the exposition of the paper. Part of this work is from a paper previously circulated under the title: “Sunspot rational belief structures: anonymity and endogenous uncertainty”.