Archives 2024-2025

• September 22nd    : Edi Karni (Johns Hopkins University )

Title :  Decisions and Discovery: A Non-Bayesian Perspective

Location: Maison des Sciences Économiques, room S16

Summary:  The paper explores a new, non-Bayesian, approach to modeling choice behavior of decision maker's who is aware that there may exist potential outcomes of his actions of which he is not aware. The new approach suggests an adaptation of Ewens (1972) generalization of De Morgan's (1838) formula of the probability of known and unpredictable outcomes to the context of decision making under risk, and embeds it in an expected utility model with costly actions.

• May 16th   : Guillaume Vigeral (Université Paris-Dauphine )

Title :  Structure of the sets of Nash equilibria of finite games; applications to the complexity of some decision problems in game theory

Location: Maison des Sciences Économiques, room S17

Summary: The set of Nash equilibrium payoffs of a finite game is always non 

empty, compact and semialgebraic. We show that, for 3 players or more, 

the reverse also holds: given E a subset of R^N that is non empty, 

compact and semialgebraic, one constructs a finite N player game such 

that E is its set of equilibrium payoffs. 

We apply this result to understand the complexity class of some natural 

decision problems on finite games.

• April 25th  : Michael Mandler (Royal Holloway University of London)

Title : Randomization in experiments and the merging of recommendations

Location: Maison des Sciences Économiques, room S17

Summary:  A random assignment of treatments to experimental subjects allows researchers with diverse priors to come to near agreement on which treatments are optimal. The result assumes that priors on data observations are mutually absolutely continuous and ratios of beliefs are bounded. Existing work shows that researchers can commit ex ante to the recommendations of randomized control trials but not that researchers will interim agree once data arrive. A probability dilation thus appears: researchers will agree ex ante and ex post but not always ex interim. Agreement is even more difficult with deterministic experiments: researchers can then fail to nearly agree on recommendations even when they agree on the probabilities of experimental results. Finally, if a maxmin rather than a unanimity rationale for randomization is used then rankings can be dynamically inconsistent.

• April 11th  : Antonin Macé (PSE)

Title : Repeated Majority Voting

Location: Maison des Sciences Économiques, room S17

Summary:  We propose a general model of repeated voting in committees and study equilibrium behavior under alternative majority rules. We find that repetition may significantly increase the efficiency of majority voting through a mechanism of intertemporal logrolling, agents sometimes voting against their immediate preference to benefit the group’s long-term interest. In turn, this affects the comparison of majority rules, which may differ significantly relative to the static setting. The model provides a rationale for the use of super-majority rules, while accounting for the prevalence of consensus in committee voting.

• March 28th  : Dinko Dimitrov (Saarland University)

Title : Incomplete Information and Matching of Likes: A Mechanism Design Approach

Location: Maison des Sciences Économiques, room S17

Summary: 

We employ a mechanism design approach and study the implementability of stable matchings in a two sided market model with one sided incomplete information. Firms' types are assumed to be publicly known, while workers' types are private information. A mechanism generates a matching and a public announcement at each reported profile of workers' types. We show that, when agents' preferences are increasing in the types of their matched partner, the assortative matching mechanism publicly announcing the set of reported types is incentive compatible. This mechanism fails to be incentive compatible when we allow for either private verification of types or incompleteness of information on both sides of the market.

• March 14th  : Pamela Bombarda (Cergy) - 

Joint seminar with the "Rencontres du CES" series

Title : Rules of Origins Relaxation and Regional Supply Chains: Evidence from Europe (with E. Gamberoni and I. Iodice)

Location: Maison des Sciences Économiques, room S17

Summary:  Free trade agreements (FTAs) incorporate regulations regarding rules of origin (RoO) and cumulation. RoO regulations, by restricting the use of inputs outside the FTA, can affect the flow of intermediates in supply chains. We construct a new database to assess the effects of RoO, enabling us to explore two major events that led to RoO relaxation in the European context: PECS, which provided the possibility of cumulating stages of production across the European Union’s FTA peripheral partners, and EU enlargement, which eliminated RoO altogether. Our results show that the progressive reduction in RoO had a sizeable impact on reshaping regional and international supply chains. Across both episodes, we estimate consistent elasticities, indicating that a 1% increase in the value requirement restriction before relaxation corresponds to an intermediate import increase ranging from 0.3% to 0.7% from countries where RoO restrictions have been lifted.

• March 14th  : Pamela Bombarda (Cergy) - 

Joint seminar with the "Rencontres du CES" series

Title : Rules of Origins Relaxation and Regional Supply Chains: Evidence from Europe (with E. Gamberoni and I. Iodice)

Location: Maison des Sciences Économiques, room S17

Summary:  Free trade agreements (FTAs) incorporate regulations regarding rules of origin (RoO) and cumulation. RoO regulations, by restricting the use of inputs outside the FTA, can affect the flow of intermediates in supply chains. We construct a new database to assess the effects of RoO, enabling us to explore two major events that led to RoO relaxation in the European context: PECS, which provided the possibility of cumulating stages of production across the European Union’s FTA peripheral partners, and EU enlargement, which eliminated RoO altogether. Our results show that the progressive reduction in RoO had a sizeable impact on reshaping regional and international supply chains. Across both episodes, we estimate consistent elasticities, indicating that a 1% increase in the value requirement restriction before relaxation corresponds to an intermediate import increase ranging from 0.3% to 0.7% from countries where RoO restrictions have been lifted.

• March 7th  : Simon Finster (CREST)

Title : TBA

Location: Maison des Sciences Économiques, room S17

Summary:  TBA

• February 21st  : Ying He (University of Southern Denmark )

Title : Two-Stage Evaluation Model for Decision Making under Ambiguity

Location: Maison des Sciences Économiques, room S17

Summary:  In this paper, a two-stage evaluation (TSE) model for decision making under ambiguity is proposed. Events in state space are classified into risky and ambiguous events, which correspond to different types of uncertainty generated by different sources. In this TSE model, uncertainty of two different types are evaluated by DM in different stages. In the first stage, DM evaluates more uncertain consequences of an act locally by applying local subjective expected utility (SEU) models, which are then embedded into the second stage evaluation based on SEU defined globally over all events. To axiomatize such a model, Kopylov (2007)’s “small” domain SEU over risky acts is extended to both risky and non-risky(ambiguous) acts. When evaluating a risky act, TSE model reduces to Savage’s SEU with one stage. When evaluating an ambiguous act, local SEU with a different uncertainty aversion defined on ambiguous events gives TSE model some flexibility in describing preferences. It can be shown that TSE model can accommodate Ellsberg’s paradoxes and Machina’s paradoxes in the literature (Ellsberg 1961, Machina 2009, 2014). When applied to portfolio selection problem, TSE model enjoys some nice properties other models do not have.

• February 14th   : Franz Dietrich  (CES  )

Title :  The impossibility of non-manipulable probability aggregation

Location: Maison des Sciences Économiques, room S17

Summary:  

A probability aggregation rule assigns to each profile of probability functions across a group of individuals (representing their individual probability assignments to some propositions) a collective probability function (representing the group’s probability assignment). The rule is “non-manipulable” if no group member can manipulate the collective probability for any proposition in the direction of his or her own probability by misrepresenting his or her probability function (“strategic voting”). We show that, except in trivial cases, no probability aggregation rule satisfying two mild conditions (non-dictatorship and consensus preservation) is non-manipulable.

• January 31st  : Georges Zaccour  (GERAD HEC Montréal )

Title : Payment schemes for finitely repeated Prisoner's Dilemma games

Location: Maison des Sciences Économiques, room S17

Summary: 

We consider finitely repeated Prisoner's Dilemma game and propose a method of sustaining cooperation as an ε-equilibrium in limited retaliation behavior strategies. The main feature of this strategy is that the punishment of a deviated player does not necessarily last until the end of the game. The duration of punishment depends on the stage when deviation happens, and it is not uniquely defined. We propose two payment schemes along the cooperative trajectory to sustain cooperation based on these limited retaliation strategies. If the payments in the game are organized following these schemes, when they exist, then players have no incentive to deviate and cooperation is sustainable.

Keywords: Prisoner's Dilemma; Repeated Games; Limited Retaliation; Cooperation; Payment Schemes.

• September 12th : Yossi Spiegel (Coller School of Management, Tel Aviv University) 

Title : A Dynamic Model of Predation

Location and time: This session is organized jointly with the reading group "Networks and Games" note that it takes place on  Thursday, 3 pm and the location is the conference room on the 6th floor at the Maison des Sciences Economiques. 

Summary:  Growing concern about the market power of big tech giants has led to renewed interest in predatory behavior. We study the feasibility and profitability of predation in a dynamic environment, using a parsimonious infinite- horizon, complete information setting in which an incumbent repeatedly faces potential entry. When a rival enters, the incumbent chooses whether to ac- commodate or predate it; the entrant then decides whether to stay or exit. We show that there always exists a Markov perfect equilibrium, which can be of three types: accommodation, monopolization, and recurrent predation. We then analyze and compare the welfare e§ects of di§erent antitrust policies.

• September 20th : Konstantinos V. Katsikopoulos (University of Southampton)

Title : Cognitive Operations:  Models that Open the Black Box and Predict our Decisions  

Location: Maison des Sciences Économiques, room S17

Summary:  Improving human behavior requires first understanding it. Can mathematical models help provide such understanding? Yes. Cognitive Operations performs a systematic examination of two main approaches to modeling human decision making: optimization and simple heuristics. The approaches are discussed by focusing on general types of decisions—under risk, under uncertainty, strategic interaction and inventory control—and by drawing on economics, psychology and artificial intelligence. Cognitive Operations is committed to supporting academics and practitioners who seek to select a modeling approach that suits the operational decision at hand. It shows how to build models and employs clear criteria for assessing them. For a model to open the black box it must specify the cognitive processes that lead to the observed decisions. To predict decisions means to fix a model in one context and to test it in another. The comparative assessment of optimization and heuristic models serves scientific pluralism and leads to surprising insights. The studies in Cognitive Operations zoom in on bounded rationality, a field pioneered by Herb Simon, a founder of behavioral economics, cognitive psychology as well as artificial intelligence. They are useful complements to mathematical, conceptual and empirical studies of human decision making. It is possible to open the black box and predict our decisions.

• September 27th: Evan Piermont (Royal Holloway, University of London )

Title : Modeling the Modeler: A Normative Theory of Experimental Design

Location: Maison des Sciences Économiques, room S17

Summary:  We consider an analyst whose goal is to identify a subject’s utility function through revealed preference analysis. We argue the analyst’s preference about which experiments to run should adhere to three normative principles: The first, Structural Invariance, requires that the value of a choice experiment only depends on what the experiment may potentially reveal. The second, Identification Separability, demands that the value of identification is independent of what would have been counterfactually identified had the subject had a different utility. Finally, Information Monotonicity asks that more informative experiments are preferred. We provide a representation theorem, showing that these three principles characterized Expected Identification Value maximization, a functional form that unifies several theories of experimental design. We also study several special cases and discuss potential applications.

• October 11th : Nicola Botta (Pottsdam Institute for Climate impact research  )

Title : Trustable Pareto optimal controls with FP

Location: Maison des Sciences Économiques, room S17

Summary:  We  combine numeric and symbolic methods to accelerate first-principles simulations and enable optimisation of fusion confinement designs, building a reliable and versatile toolset for performance optimisation of strongly coupled physical systems with a large parameter space, and apply it to explore reliable fusion designs.”

• November 29th: Erwin Ooghe (KU Leuven)

Title : Fairness gaps for earnings tax design

Location: Maison des Sciences Économiques, room S17

Summary: In a setting with skill and preference heterogeneity, we characterize a family of social welfare measures that aggregate fairness gaps, dened as the dierence between the money-metric utilities that individuals have and the money-metric utilities they should have in a fair society. Each welfare measure can be decomposed into government revenues (size), excess burden (ineciency), and unfair inequality (inequity). As a proof of concept, we evaluate four hypothetical earnings tax reforms based on two normative parameters: the degree of unfairness aversion and the degree of compensation for productive skills.

• December 6th : Zoi Terzopoulou  (GATE)

Title : TBA

Location: Maison des Sciences écoomiques, room S17

Summary: TBA

• December 13th : Marcello Bassili  (DEPS, University of Sienna )

Title : A new approach for imprecise probabilities

Location: Maison des Sciences Économiques, room S17

Summary:  This paper introduces a novel concept of interval probability measures that enables the representation of imprecise probabilities, or uncertainty, in a natural and coherent manner. Within an algebra of sets, we introduce a notion of weak complementation denoted as ψ. The interval probability measure of an event H is defined with respect to the set of indecisive eventualities (ψ(H))c, which is included in the standard complement Hc.We characterize a broad class of interval probability measures and de- fine their properties. Additionally, we establish an updating rule with respect to H, incorporating concepts of statistical independence and de- pendence. The interval distribution of a random variable is formulated, and a corresponding definition of stochastic dominance between two ran- dom variables is introduced. As a byproduct, a formal solution to the century-old Keynes-Ramsey controversy is presented.

• January 31st : Georges Zaccour (GERAD, HEC Montreal, Canada)

Title : Payment schemes for finitely repeated Prisoner's Dilemma games

Location: Maison des Sciences Économiques, room S17

Summary

We consider finitely repeated Prisoner's Dilemma game and propose a method of sustaining cooperation as an ε-equilibrium in limited retaliation behavior strategies. The main feature of this strategy is that the punishment of a deviated player does not necessarily last until the end of the game. The duration of punishment depends on the stage when deviation happens, and it is not uniquely defined. We propose two payment schemes along the cooperative trajectory to sustain cooperation based on these limited retaliation strategies. If the payments in the game are organized following these schemes, when they exist, then players have no incentive to deviate and cooperation is sustainable.

• February 7th  :Michel Grabisch (Centre d'Economie de la Sorbonne)

Title : A polynomial view of TU-games

Location: Maison des Sciences Économiques, room S17

Summary:  We propose in this paper a polynomial representation of TU-games, and more generally set functions on a finite set. Our representation needs a countably infinite set of players and the natural ordering of finite sets of N, defined recursively. For a given basis of the vector space of games, we associate to each game v a formal polynomial of degree at most 2^n-1 whose coefficients are the coordinates of v in the given basis. By the fundamental theorem of algebra, v can be represented by the roots of the polynomial. We present some new families of games stemming from  this polynomial context, like the irreducible games, the multiplicative games and the cyclotomic games.