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

Decision theory offers a formal approach to decision making, which is often viewed and taught as the rational way to approach managerial decisions. Half a century ago it generated high hopes of capturing and perhaps replacing intuition, and providing the “right” answer in practically all managerial situations. Today it seems fair to say that decision theory has not lived up to these expectations. Behavioral science provides ample evidence that managers fail to follow the dicta of decision theory, even when these are explained to them. As a result, executives often find decision theory frustrating and useless and prefer to rely on their intuition. This paper suggests that this extreme conclusion is unwarranted and calls for a re-appraisal of decision theory. We propose that it should not always be regarded as a mathematical tool that produces the answer; rather, it can be viewed as a framework for a dialog between the decision maker and the decision theorist. In one extreme, the decision theorist studies the problem and provides the “correct’’ answer. But in another, the decision theorist only challenges the decision maker’s intuition and logic. In between, a whole gamut of possible dialogs exists, in which decision theory doesn’t replace intuition, but supports and refines it.


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

We study the interaction between multiple information designers who try to influence the behavior of a set of agents. When the set of messages available to each designer is finite, such games always admit subgame perfect equilibria. When designers produce public information about independent pieces of information, every equilibrium of the direct game (in which the set of messages coincides with the set of states) is an equilibrium with larger (possibly infinite) message sets. The converse is true for a class of Markovian equilibria only. When designers produce information for their own corporation of agents, pure strategy equilibria exist and are characterized via an auxiliary normal form game. In an infinite-horizon multi-period extension of information design games, a feasible outcome which Pareto dominates a more informative equilibrium of the one-period game is supported by an equilibrium of the multi-period game.

Mots clés : Bayesian persuasion , information design , sharing rules , splitting games , statistical experiments.


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

Les économistes ont coutume de distinguer entre une composante positive et une composante normative de leurs travaux, ce qui est une singularité de leur discipline, car cette distinction n'a pas de répondant exact dans les autres sciences sociales. Elle a fortement évolué au cours du temps et les différentes manières de la concevoir aujourd'hui en reflètent l'histoire. On se propose ici d'en retracer les origines et les premières formes, de l'économie politique classique anglaise de la première moitié du XIXe siècle jusqu'à l'apparition de l'économie du bien-être dans la première moitié du XXe siècle. Ce parcours séquentiel vise aussi à identifier les positions les plus représentatives et les arguments invoqués pour les soutenir, en préparant ainsi une discussion qui serait moins historique et plus strictement conceptuelle.

Mots clés : économie positive et économie normative, jugements de valeur, thèse de Hume, objectivité au sens de Weber, économie du bien-être, John Stuart Mill, John Neville Keynes, Lionel Robbins, positive economics and normative economics, value judgments, Hume's thesis, objectivity in


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

The standard, Bayesian account of rational belief and decision is often argued to be unable to cope properly with severe uncertainty, of the sort ubiquitous in some areas of policy making. This paper tackles the question of what should replace it as a guide for rational decision making. It defends a recent proposal, which reserves a role for the decision maker’s confidence in beliefs. Beyond being able to cope with severe uncertainty, the account has strong normative credentials on the main fronts typically evoked as relevant for rational belief and decision. It fares particularly well, we argue, in comparison to other prominent non-Bayesian models in the literature.

Mots clés : Confidence, Decision Under Uncertainty, Belief, Rationality


Départements : Economie et Sciences de la décision

This paper analyzes, empirically and theoretically, the link between capital inflows and the quality of economic institutions. Starting with the example of Southern European countries (Spain, Portugal, Italy and Greece), we show that they experienced a significant decline in the quality of their institutions in the run-up to the euro currency, a period of cheap external funding and large capital inflows. We confirm this joint pattern of capital flows and institutional decline in a large panel of countries since the mid-1990s. We then develop an open-economy model of the "soft budget constraint" syndrome wherein persistently cheap funding from abroad (i) raises the prevalence of extractive projects and (ii) expands their support by the (benevolent) government ex post. While the government may in principle limit the prevalence of extractive projects ex ante, we show that the incentives to do so is limited when foreign borrowing is cheap.

Mots clés : Institutions, current account


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

Relying on a literal interpretation of Weber's law in psychophysics, we show that a simple condition of independence across good categories implies the Cobb-Douglas preferences.

Mots clés : Cobb-Douglas, Weber's Law, Semi-Order


Départements : Economie et Sciences de la décision

This paper shows that bailouts of private agents can optimally take the form of the purchase of a defaulting asset, even if this also means paying off external asset holders. When anticipated, this form of bailouts leads to an endogenous implicit guarantee, where even an intrinsically worthless asset may be traded at a positive price. In the presence of borrowing constraints and imperfectly observable private liquidity needs, direct transfers are imperfect so that, when more constrained agents are also more exposed to a given asset, the compensation through asset purchases becomes optimal. I then show that this possibility of implicit guarantee is amplified by other frictions as risk-shifting and ultimately leads to a coordination problem for selecting stores of liquidity. Finally, I derive policy implications for financial regulation and international capital flows.

Mots clés : Implicit guarantees, bailouts, intrinsically worthless assets


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

We revisit well-known models of learning in which a sequence of agents make a binary decision on the basis of a private signal and additional information. We introduce efficiency measures, aimed at capturing the speed of learning in such contexts. Whatever the distribution of private signals, we show that the learning efficiency is the same, whether each agent observes the entire sequence of earlier decisions, or only the previous decision. We provide a simple necessary and sufficient condition on the signal distributions under which learning is efficient. This condition fails to hold in many prominent cases of interest. Extensions are discussed.


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

Equity crowdfunding has recently become available and is quickly expanding. Concerns have been raised that investors ('backers') may be following the crowd 'too much' and making investments ('pledges') based on past investments rather than private information. We construct a model of equilibrium rational herding where uninformed investors follow signals generated by in formed investors with private information and a public belief generated by all past pledges. We show that large investments provide positive public information about the project's quality, whereas periods of absence of investment provide negative information. An information cascade is shown to occur only if not enough positive signals are generated. We then empirically analyse a large number of pledges from a leading European equity crowdfunding platform. We show that a pledge is strongly affected by both the size of the most recent pledge, and the time elapsed since the most recent pledge. For pledges that are not adjacent in the order of arrivals, the correlation between their sizes is still positive, but after being separated by two or more intervening pledges the correlation is no longer statistically significant. The effects are strongest for less-informed investors, and in some specifications the effects are strongest at the early stage of a campaign. We find similar results in IV analysis. Results are consistent with our model and inconsistent with some alternative models

Mots clés : Equity Crowdfunding, Herding


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

We consider a Bayesian persuasion problem where the persuader and the decision maker communicate through an imperfect channel which has a fixed and limited number of messages and is subject to exogenous noise. Imperfect communication entails a loss of payoff for the persuader. We establish an upper bound on the payoffs the persuader can secure by communicating through the channel. We also show that the bound is tight: if the persuasion problem consists of a large number of independent copies of the same base problem, then the persuader can achieve this bound arbitrarily closely by using strategies which tie all the problems together. We characterize this optimal payoff as a function of the information-theoretic capacity of the communication channel


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