Articles publiés

1. Bayesian social aggregation with almost-objective uncertainty,

Elise Flore Tchouante and Marcus Pivato, Theoretical economics, 2024. https://econtheory.org/ 

Abstract:  We consider collective decisions under uncertainty, gen- *when agents have eralized Hurwicz preferences, a broad class allowing many different ambiguity attitudes, including subjective expected utility preferences. We consider sequences of acts that are “almost-objectively uncertain” in the sense that asymptotically, all agents almost-agree about the probabilities of the underlying events. We impose a Pareto axiom which applies only to asymptotic preferences along such almost-objective sequences. This axiom implies that the social welfare function is *utilitarian, but it does not impose any constraint on collective beliefs. Obversely, a Pareto axiom for “dichotomous” acts implies that collective beliefs are contained in the closed convex hull of individual beliefs, but imposes no constraints on the social welfare function. Neither axiom imposes any relationship between individual and collective ambiguity attitudes. 

2. Bayesian Social Aggregation With Non-Archimedean Utilities and Probabilities  

Elise Flore Tchouante and Marcus Pivato, Economics Theory, 2023   https://doi.org/10.1007/s00199-023-01509-w  

Abstract: We consider social decisions under uncertainty. We show that the ex ante social preference order satisfies a Pareto axiom with respect to ex ante individual preferences, along with an axiom of Statewise Dominance, if and only if all agents admit subjective expected utility (SEU) representations, and furthermore the social planner is a utilitarian. The social utility function is the sum of the individual utility functions. In these SEU representations, the utility functions take values in an ordered abelian group, and probabilities are represented by order-preserving automorphisms of this group. This group may be non-Archimedean; this allows the SEU representations to encode lexicographical preferences and/or infinitesimal probabilities. 

3. Pure-strategy Nash equilibrium in the spatial model with valence: existence and characterization,  

Elise Flore Tchouante, Mathieu Martin, Zephirin Nganmeni and Ashley Piggins,  Public choice, 2022,  https://doi.org/10.1007/s11127-021-00936-4  

Abstract: Pure strategy Nash equilibria almost never exist in spatial majority voting games when the number of positional dimensions is at least two. This is due to the fact that the majority core is typically empty when there is more than one positional dimension. In the general setting of proper spatial voting games, we study the existence of equilibrium when one candidate has a valence advantage over the other. When we consider these games, a valence equilibrium can exist which is not in the core, and a point in the core need not be a valence equilibrium. In this paper, we characterize the entire set of valence equilibria for any proper spatial voting game. We complement this by deriving a simple inequality that is both necessary and sufficient for the existence of a valence equilibrium. This inequality refers to the radius of a new concept, the b-yolk, and we prove that a $b$-yolk always exists in a spatial voting game.