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

This chapter briefly reviews the present state of judgment aggregation theory and tentatively suggests a future direction for that theory. In the review, we start by emphasizing the difference between the doctrinal paradox and the discursive dilemma, two idealized examples which classically serve to motivate the theory, and then proceed to reconstruct it as a brand of logical theory, unlike in some other interpretations, using a single impossibility theorem as a key to its technical development. In the prospective part, having mentioned existing applications to social choice theory and computer science, which we do not discuss here, we consider a potential application to law and economics. This would be based on a deeper exploration of the doctrinal paradox and its relevance to the functioning of collegiate courts. On this topic, legal theorists have provided empirical observations and theoretical hints that judgment aggregation theorists would be in a position to clarify and further elaborate. As a general message, the chapter means to suggest that the future of judgment aggregation theory lies with its applications rather than its internal theoretical development.

Mots clés : Judgment Aggregation Theory, Logical Aggregation Theory, Law and Economics, Doctrinal Paradox, Discursive Dilemma, Canonical Theorem of Judgment Aggregation Theory, Premiss-Based Versus Conclusion-Based Method, Collegiate Courts, Issue-Based Versus Case-Based Adjudication Method


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

Whereas many others have scrutinized the Allais paradox from a theoretical angle, we study the paradox from an historical perspective and link our findings to a suggestion as to how decision theory could make use of it today. We emphasize that Allais proposed the paradox as a normative argument, concerned with "the rational man" and not the "real man", to use his words. Moreover, and more subtly, we argue that Allais had an unusual sense of the normative, being concerned not so much with the rationality of choices as with the rationality of the agent as a person. These two claims are buttressed by a detailed investigation – the first of its kind – of the 1952 Paris conference on risk, which set the context for the invention of the paradox, and a detailed reconstruction – also the first of its kind – of Allais's specific normative argument from his numerous but allusive writings. The paper contrasts these interpretations of what the paradox historically represented, with how it generally came to function within decision theory from the late 1970s onwards: that is, as an empirical refutation of the expected utility hypothesis, and more specifically of the condition of von Neumann-Morgenstern independence that underlies that hypothesis. While not denying that this use of the paradox was fruitful in many ways, we propose another use that turns out also to be compatible with an experimental perspective. Following Allais's hints on "the experimental definition of rationality", this new use consists in letting the experiment itself speak of the rationality or otherwise of the subjects. In the 1970s, a short sequence of papers inspired by Allais implemented original ways of eliciting the reasons guiding the subjects' choices, and claimed to be able to draw relevant normative consequences from this information. We end by reviewing this forgotten experimental avenue not simply historically, but with a view to recommending it for possible use by decision theorists today.

Mots clés : Allais Paradox, Decision Theory, Expected Utility Theory, Experimental Economics, Positive vs Normative, Rationality, 1952 Paris Conference, Allais, Von Neumann and Morgenstern, Samuelson, Savage


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

Reports of the Intergovernmental Panel on Climate Change (IPCC) employ an evolving framework of calibrated language for assessing and communicating degrees of certainty in findings. A persistent challenge for this framework has been ambiguity in the relationship between multiple degree-of-certainty metrics. We aim to clarify the relationship between the likelihood and confidence metrics used in the Fifth Assessment Report (2013), with benefits for mathematical consistency among multiple findings and for usability in downstream modeling and decision analysis. We discuss how our proposal meshes with current and proposed practice in IPCC uncertainty assessment.

Mots clés : confidence; uncertainty reporting; climate change


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

Many decision situations involve two or more of the following divergences from subjective expected utility: imprecision of beliefs (or ambiguity), imprecision of tastes (or multi-utility), and state dependence of utility. Examples include multi-attribute decisions under uncertainty, such as some climate decisions, where trade-offs across attributes may be state dependent. This paper proposes and characterises a model of uncertainty averse preferences that can simultaneously incorporate all three phenomena. The representation supports a principled separation of (imprecise) beliefs and (potentially state-dependent, imprecise) tastes, and we pinpoint the axiom that ensures such a separation. Moreover, the representation supports comparative statics of both beliefs and tastes, and is modular: it easily delivers special cases involving various combinations of the phenomena, as well as state-dependent multi-utility generalisations of popular ambiguity models.

Mots clés : state-dependent utility, uncertainty aversion, multiple priors, ambiguity, imprecise tastes, multi-utility


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

In this article, we investigate strategic information transmission over a noisy channel. This problem has been widely investigated in Economics, when the communication channel is perfect. Unlike in Information Theory, both encoder and decoder have distinct objectives and choose their encoding and decoding strategies accordingly. This approach radically differs from the conventional Communication paradigm, which assumes transmitters are of two types: either they have a common goal, or they act as opponent, e.g. jammer, eavesdropper. We formulate a point-to-point source-channel coding problem with state information, in which the encoder and the decoder choose their respective encoding and decoding strategies in order to maximize their long-run utility functions. This strategic coding problem is at the interplay between Wyner-Ziv’s scenario and the Bayesian persuasion game of Kamenica-Gentzkow. We characterize a single-letter solution and we relate it to the previous results by using the concavification method. This confirms the benefit of sending encoded data bits even if the decoding process is not supervised, e.g. when the decoder is an autonomous device. Our solution has two interesting features: it might be optimal not to use all channel resources; the informational content impacts the encoding process, since utility functions capture preferences on source symbols.


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

Contacts  

Département Economie et Sciences de la Décision

Campus HEC Paris
1, rue de la Libération
78351 Jouy-en-Josas cedex
France

Faculté  

Eric MENGUS

Economie - Sciences de la Décision

Voir le CV

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