Groupe d'Analyse et de Théorie Economique
Le "GATE Lyon-Saint-Etienne" (Groupe d'Analyse et de Théorie Economique) est une Unité Mixte de Recherche (UMR5824) rattachée au CNRS Sciences humaines & sociales, à l'Université Lumière-Lyon 2, à l'Université Jean Monnet-St-Etienne et à l'emlyon.
À la une
Voir toutes les actualitésArno Riedl, visiting fellow
Call for GATE PhD
Le GATE recrute
Deuxième édition du GATE on the Docks
Antoinette Baujard sur France Culture
Tribune dans Le Monde, par Sonia Paty
Prochains évènements
Retour à l'agendaMultiwinner voting aims to select a subset of alternatives (a committee) from a larger set of admissible alternatives, according to the votes cast by voters. We consider in this paper that each voter is endowed with a preference order in which the alternatives are ranked from the best to the worst. In this setting, we can define committee scoring rules as multiwinner analogues of positional scoring rules which constitute a well-known subclass of single-winner voting rules. A special class of committee scoring rules – (weakly) separable scoring rules – have gained considerable attention recently. Under this class, when the aim is to select a committee of size exactly k, we can first compute a separate score for each alternative using a single-winner scoring rule and then pick the k alternatives with the top scores. When the underlying single-winner scoring rule does (not) depend on the size k of the target committee then the rule is referred to as (weakly) separable. In this paper, we consider a model of multiwinner voting using (weakly) separable scoring rules where, moreover, alternatives have certain attributes and for each attribute there is a minimal desired number that the selected committee should fit. In this setting, enforcing attribute constraints on the winning committee must naturally have a cost since the feasible space of committees becomes smaller and hence the optimal score may decrease. We measure this cost, that we refer to as the price of diversity, by considering the ratio between the score of the optimal unconstrained committee and the score of the optimal constrained committee. We study to what extent the price of diversity changes regarding the choosen rule.
A growing body of evidence now shows that overconfidence provides important interpersonal benefits in strategic interactions. Building on this literature, we investigate whether overconfidence can emerge as a strategy in performance-based competition. More specifically, we test whether overconfident individuals can achieve higher payoffs than their well-calibrated counterparts by being more successful at deterring their opponents from entering the competition. In addition, we examine whether individuals are sophisticated about the malleability of their beliefs by engaging in motivated reasoning primarily when deterrence is possible. Finally, we study how the possibility to deter affects individuals’ information acquisition strategy.
Abstract :
Traditional models, such as the mean-variance framework, miss two crucial, related factors: richness of uncertainty and more realistic preferences. This project aims to study portfolio optimization and related problems, in a dynamic setting for an agent concerned by the occurrence of exogenous rare events, and who can access a wide class of investment products. The project adopts three novel approaches: incorporating heterogeneous preferences and a variety of assets (options and other derivatives) in a portfolio optimization model, exploring non-standard preferences such as loss aversion in dynamic settings, and analyzing portfolio responses to rare and sudden shocks, such as market crashes or pandemics. Methodologies employed include recursive preference frameworks and stochastic differential utility models, which disentangle risk aversion from intertemporal elasticity of substitution. Theoretical insights will be translated into practical numerical applications to assess their relevance to real-world financial markets. This research bridges the gap between risk and decision theory and the complex dynamics of financial markets, contributing to a deeper understanding of optimal portfolio design under ambiguity.
Abstract :
This project introduces a new class of solutions for collective decision-making problems under uncertainty such as the climate crisis, health emergencies such as COVID-19, and the economic impacts of technological disruptions. In particular, it examines the relationship between preference aggregation across individuals in collective decisions and across possible events for a single individual who does not know which event will occur. More precisely, we assume that agents have a utility for each option, which may vary from one event to another. Agents can aggregate their utilities across different events into a single utility using an aggregation function. The objective is to explore the connection between how utilities are aggregated across agents for a given option in a given event and how they are aggregated across events for a given option and a given agent. For example, if a couple consistently chooses to go to a restaurant regardless of the weather, the collective choice method should also recommend going to the restaurant when considering their overall preferences before knowing the weather. To achieve this, we adopt an axiomatic approach centered on a consistency principle: if the same option is socially chosen for two distinct utility profiles corresponding to two distinct events, then this option should also be chosen for the utility profile resulting from their aggregation. This axiom, combined with Unanimity, Anonymity, and Neutrality, ensures that each agent’s preferences across different events are aggregated in the same manner as the preferences of different agents within the same event. Furthermore, by incorporating additional axioms and an algebraic approach, we characterize various interesting solutions.
We study the role of self-promotion and career advice in sustaining gender differences in labor market outcomes. We conduct an online experiment in which “advisers” advise “workers” to choose between a more ambitious and a less ambitious task based on the worker’s subjective self-assessment. We find that women have lower self-assessments and receive less ambitious career advice as a result. We also show that these gender differences are similar for both quantitative and qualitative self-assessments, and that the gender difference in advice received can be mitigated by informing advisers of the workers’ true performance or of the gender gap in self-promotion.
Although altruistic behavior is well established, recent evidence suggests that it is only partly genuine, reflecting instead the desire to appear fair, either to themselves or to others.
In a lab experiment with 288 participants, we measured the extent of posturing and its relationship with other dimensions of social preferences. We implement a within-subject design that uses the different variations of the modified dictator game in Blanco et al. (2011) to elicit inequality concerns in Other-Other allocations and in Self-Other allocations in several cases: solely allocation (modified dictator game), under plausible deniability (moral wiggle room), and with the possibility to exert positive and negative reciprocity towards the allocator when in the role of the recipient. For the measurement of the moral wiggle room, our instrument allows not only to identify wrigglers, but also to convey an estimate of their posturing degree. In fact, departing from most of the tasks in the literature (based on the standard dictator game), our experimental protocol allows subjects to trade off their concern for money and reputational incentives at the margin without fully revealing their type.
More importantly, our design allows us to classify subjects along two dimensions: social image concern and deontological preferences. Once classified in this way, subjects show consistent, yet different, patterns of moral wiggle room and reciprocity. Overall, the use of the moral wiggle room is not prevalent. Only 38% of our subjects are less altruistic when their choice is hidden by the presence of a random draw than when it is fully observable. Interestingly those classified as Kantians (47% of our sample) are more prone to use the moral wiggle room than consequentialists (28%). While 37% of Kantians are moral wigglers, for consequentialists they represent only 29% of their group. Additionally, Kantians are more reciprocal in the intensive margin, but more likely to avoid punishing others. Moreover, non-reciprocal Kantians are often moral wrigglers.
Derniers articles parus
Voir toutes les publicationsArticle dans une revue
2025
- ref_biblio
- Yann Braouézec, Keyvan Kiani. Preventing Price-Mediated Contagion Due to Fire Sales Externalities : Strategic Foundations of Macroprudential Regulation. Operations Research, 2025, 73 (1), 40-60 p. ⟨10.1287/opre.2023.0237⟩. ⟨hal-04817941⟩
- Accès au bibtex
-
- ref_biblio
- Jiakun Zheng, Hélène Couprie, Astrid Hopfensitz. Collective risk-taking by couples : Individual vs household risk. Theory and Decision, In press, 31 p. ⟨10.1007/s11238-024-10021-z⟩. ⟨hal-04911748⟩
- Accès au bibtex
-