Yusuke YAMAGUCHI will defend his thesis on Tuesday 23th September 2025 at 02:00 PM (Online)
Title: Essays in Economic Theory
Supervisor: Professor David MARTIMORT
To attend the conference, please contact the secretariat of the TSE Doctoral school.
Memberships are:
- David MARTIMORT : Professor in Economics, Ecole TSE, Supervisor
- Andrea ATTAR : Professor in Economics, Ecole TSE, Examinateur
- Catherine BOBTCHEFF : Professor in Economics, Paris School of Economics Rapporteure
- Joaquin POBLETE : Associate in Economics, PUC School of Management Rapporteur
- Takuro YAMASHITA : in Economics, University of Osaka Examinateur
Abstract :
This thesis comprises three chapters. Chapter 1 analyzes bilateral bargaining mediated by an intermediary who is biased—sharing interests with one party—and lacks both commitment and enforcement power. By comparing the upper bounds of achievable expected social surplus in the mediated bargaining game and in the seller-offer bargaining game, I show that, in the second-best scenario, a biased intermediary can yield a higher expected surplus in equilibrium, provided the cost of employing the intermediary is sufficiently small. This result offers a theoretical rationale for the widespread use of biased intermediaries in practice, even when their bias is common knowledge.
Chapter 2 examines a standard moral hazard setting in which the agent exhibits dual risk-aversion—that is, he overweights the probability of bad outcomes relative to objective probabilities.
I show that, under some regularity conditions, the cost-minimizing contract for each inducible action takes the form of a debt contract: the wage is constant up to a certain output level and then increases at the same rate as output thereafter. Accordingly, the result offers a new explanation for the prevalence of simple linear contracts in practice.
Chapter 3, which is based on the joint work with Takuro Yamashita, studies a stylized model of adverse selection. I show that under certain conditions, the unique equilibrium outcome is no trade, regardless of the richness of the soft
information structure. In contrast, when hard information is available, there exists an equilibrium in which trade occurs and the seller obtains a positive expected payoff. Taken together, these results underscore the importance of explicitly accounting for the availability of hard information when considering informationally robust predictions.
