A Cognitive Model of Individual Well-Being

I. GILBOA, D. Schmeidler

Social Choice and Welfare

2000, vol. 12, pp.269-288

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

An Experimental Study of Updating Ambiguous Beliefs

M. Cohen, I. GILBOA, J. Jaffray, D. Schmeidler

Risk, Decision, and Policy

2000, vol. 5, pp.123-133

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

An improved version of a theorem concerning finite row-column exchangeable arrays

M. SCARSINI, D. Capello, B. Bassan

Commentationes Mathematicae Universitatis Carolinae

2000, vol. 41, pp.197-198

Départements : Economie et Sciences de la décision

Case-Based Knowledge and Induction

I. GILBOA, D. Schmeidler

IEEE Transactions on Systems, Man, and Cybernetics - A

2000, vol. 30, pp.85-95

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

Does Optimization Imply Rationality?



2000, vol. 124, pp.73-111

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

The relations between rationality and optimization have been widely discussed in the wake of Herbert Simon's work, with the common conclusion that the rationality concept does not imply the optimization principle. The paper is partly concerned with adding evidence for this view, but its main, more challenging objective is to question the converse implication from optimization to rationality, which is accepted even by bounded rationality theorists. We discuss three topics in succession: (1) rationally defensible cyclical choices, (2) the revealed preference theory of optimization, and (3) the infinite regress of optimization. We conclude that (1) and (2) provide evidence only for the weak thesis that rationality does not imply optimization. But (3) is seen to deliver a significant argument for the strong thesis that optimization does not imply rationality

Existence and Regularity of Partially Revealing Rational Expectations Equilibrium in Finite Economies

A. Villanacci, A. CITANNA

Journal of Mathematical Economics

août 2000, vol. 34, n°1, pp.1-26

Départements : Economie et Sciences de la décision

We consider an incomplete financial market exchange economy with nominal assets and a finite number of traders, goods, states and signals. In this framework, we prove the existence and regularity of rational expectations equilibria for any informational structure derived from prices. We provide a proof that completes the characterization of existence of equilibrium in these economies, in the following sense: while Polemarchakis and Siconolfi [Polemarchakis, H., Siconolfi, P., 1993. Asset markets and the information revealed by prices. Economic Theory, Vol. 3, pp. 645-661.] show existence only of fully nonrevealing equilibrium, and Rahi [Rahi, R., 1995. Partially revealing rational expectations equilibria with nominal assets. Journal of Mathematical Economics, Vol. 24, pp. 137-146.] finds partially revealing equilibria for all economies satisfying a restrictive condition on the traders' equilibrium information structure, we dispense with Rahi's condition, and offer a strategy of proof that applies directly to all cases of revelation. Our proof of existence is based on homotopy methods. Given the way we construct our proof, we can easily link the asymmetric information model to the linear restricted participation models. We show how to apply the "Cass trick" in asymmetric information economies to control for asset prices, even if all agents are restricted, that is, partially informed

Incomplete Markets, Allocative Efficiency, and the Information Revealed by Prices

A. Villanacci, A. CITANNA

Journal of Economic Theory

février 2000, vol. 2, n°90, pp.222-253

Départements : Economie et Sciences de la décision

We compare rational expectations equilibria with different degrees of information revelation through prices. These equilibria arise in a two-period exchange economy with finitely many states and signals, multiple commodities and incomplete financial markets for nominal assets. We show that there are always equilibria where information is redundant in the sense of being of no value to the uninformed traders. We give conditions under which for a generic set of economies, parametrized by endowments and utilities, there exist open sets of equilibria for which allocative and informational efficiency are independent, with implications for monetary policy

Les préférences révélées et la formation de la théorie de la demande


Revue Economique

2000, vol. 51, pp.1125-1152

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

L'occasion de ce travail est fournie par le cinquantenaire de deux articles célèbres,écrits par Houthakker et par Samuelson, auxquels la théorie néo-classique duconsommateur doit en partie sa forme actuellement reçue. On situera l'apport desdeux articles dans les deux problématiques suivantes : celle des « préférencesrévélées », conçue par Samuelson en 1938, et celle, qui remonte à Pareto en 1906,de l' « intégrabilité des fonctions de demande ». On s'efforcera de comprendrepourquoi la lancinante question de l'intégrabilité n'a trouvé de solution que grâce audétour tardif et peu naturel d'une théorie des « préférences révélées ». L'articlepropose en outre une interprétation nouvelle du travail de Samuelson, qui vise à leréhabiliter contre les objections méthodologiques des commentateurs. On conclutque la notion de « préférences révélées » présente un intérêt persistant pour lathéorie contemporaine du consommateur

On the Determination of Subjective Probability by Choices

E. Karni, P. MONGIN

Management Science

2000, vol. 46, pp.233-248

Départements : Economie et Sciences de la décision, GREGHEC (CNRS)

The paper explores the uniqueness properties of the subjective probabilities in two axiomatizations of state-dependent preferences Karni, Schmeidler, and Vind's (KSV 1983) system depends on selecting an arbitrary auxiliary probability, and as such, does not guarantee the uniqueness of the derived subjective probability. However, an axiom system initially designed by Karni and Schmeidler (KS 1981) and further elaborated upon here does guarantee the desired uniqueness as well as a useful property of "stability" of the derived solution. When the preference relation displays state-independence, even the KS probabilities may not agree with those derived from the classic Anscombe-Aumann (AA 1963) theorem. However, we claim that, in this case, the KS rather than the AA probabilities are the appropriate representation of the agent's beliefs

On the number of pure strategy Nash equilibria in random games

M. SCARSINI, Y. Rinott

Games and Economic Behavior

2000, vol. 33, n°2, pp.274-293

Départements : Economie et Sciences de la décision

How many pure Nash equilibria can we expect to have in a finite game chosen at random? Solutions to the above problem have been proposed in some special cases. in this paper we assume independence among the profiles, but we allow either positive or negative dependence among the players' payoffs in a same profile. We provide asymptotic results for the distribution of the number of Nash equilibria when either the number of players or the number of strategies increases. We will show that different dependence assumptions lead to different asymptotic results