Gaëtan Fournier

Chercheur ,  Aix-Marseille Université , Faculté d'économie et de gestion (FEG)

Économétrie, finance et méthodes mathématiques
Fournier
Statut
Maître de conférences
Domaine(s) de recherche
Théorie des jeux et réseaux sociaux
Thèse
2015, Université Paris 1 Panthéon-Sorbonne
Téléchargement
CV
Contact
gaetan.fournier[at]univ-amu.fr
Adresse

AMU - AMSE
5-9 Boulevard Maurice Bourdet, CS 50498
​13205 Marseille Cedex 1

Site
https://sites.google.com/view/fourniergaetan
Résumé We study candidates' position adjustments in response to information about voters' preferences. Repositioning allows candidates to move closer to the median voter, but it incurs financial and electoral costs. In a subgame-perfect equilibrium, candidates diverge from the center ex ante if the costs of adjustment are sufficiently large. This allows them to increase the chances of a costless victory when the information is strongly in their favor. Our theory highlights a dynamic of moderation during the campaign stage in competitive elections, as well as a prominent role for minor adjustments made preemptively by the favored candidate. JEL Classification: C72, D72, D82 Model. We enrich the Downs-Hotelling framework by introducing an information shock, creating a two-stage game. The shock reveals the location of the median voter. This captures the idea that voters' aggregate preferences fluctuate over time and that their current leanings are disclosed during the electoral cam-This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Mots clés Re-positioning, Spatial voting, Imperfect information, Flip-flop
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Résumé We study a class of location games where players want to attract as many resources as possible and pay a cost when deviating from an exogenous reference location. This class of games includes political competitions between policy-interested parties and firms' costly horizontal differentiation. We find that the introduction of reference locations simplifies the set of pure-strategy equilibrium to a unique candidate which has a strong property: at most four players, the two most-left and two most-right, deviate from their reference locations. We provide necessary and sufficient conditions for the candidate to be an equilibrium. We illustrate our results in particular cases including the duopoly competition where we moderate the principle of minimal differentiation.
Mots clés Location games Spatial competition Spatial voting theory Costly product differentiation
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Résumé We study approachability theory in the presence of constraints. Given a repeated game with vector payoffs, we study the pairs of sets (A, D) in the payoff space such that Player 1 can guarantee that the long-run average payoff converges to the set A, while the average payoff always remains in D. We provide a full characterization of these pairs when D is convex and open, and a sufficient condition when D is not convex.
Mots clés Optimization, Approachability, Game Theory
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Résumé A pure Hotelling game is a spatial competition between a finite number of players who simultaneously select a location in order to attract as many consumers as possible. In this paper, we study the case of a general distribution of consumers on a network generated by a metric graph. Because players do not compete on price, the continuum of consumers shop at the closest player’s location. If the number of sellers is large enough, we prove the existence of an approximate equilibrium in pure strategies, and we construct it.
Mots clés Large games, Approximate Nash equilibria, Pure equilibria, Location games on networks, Hotelling games
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Résumé We consider a game where a finite number of retailers choose a location, given that their potential consumers are distributed on a network. Retailers do not compete on price but only on location, therefore each consumer shops at the closest store. We show that when the number of retailers is large enough, the game admits a pure Nash equilibrium and we construct it. We then compare the equilibrium cost borne by the consumers with the cost that could be achieved if the retailers followed the dictate of a benevolent planner. We perform this comparison in terms of the Price of Anarchy (i.e., the ratio of the worst equilibrium cost and the optimal cost) and the Price of Stability (i.e., the ratio of the best equilibrium cost and the optimal cost). We show that, asymptotically in the number of retailers, these ratios are bounded by two and one, respectively.
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Résumé Political campaigns influence how voters prioritize issues, which in turn impacts electoral outcomes. In this paper, we study how candidates’ communication shapes which issues prevail during the campaign, through which mechanisms, and to what extent. We develop an electoral competition model with two candidates, each endowed with exogenous platforms and characteristics. Candidates allocate strategically their communication time across two issues to maximize their expected vote shares. We find that when one candidate holds similar comparative advantages on both issues, the disadvantaged candidate communicate on a single issue to saturate the campaign with one topic and then increases the randomness of the election. The advantaged candidate has the opposite incentive and communicate on both issues, creating an asymmetry in the campaign. We show that in some cases, the campaign can become entirely centered on a single issue.
Mots clés Electoral competition, Communication time, Priming
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