Thi Hien PHAM' PhD Thesis, December 18th

December 18, 2023 Research

Thi Hien PHAM will defend her thesis on Monday, December 18 at 2pm, by ZOOM

"Essays in Microeconomic Theory"

Supervisors: Johannes HORNER and Takuro YAMASHITA

To attend the conference, please contact the secretariat Christelle Fotso Tatchum

Memberships are:

  • Johannes Horner : Professor, TSE - Toulouse Capitole University, Supervisor
  • Takuro Yamashita : Professor d’Economie, Osaka University Co-supervisor
  • Jacques Cremer : Senior researcher CNRS-TSE-R,  Advisor
  • Sarah Auster : Professor, University of Bonn, Rapporteur
  • Peter Eso : Professor, University of Oxford, Rapporteur


This thesis comprises four essays on mechanism and information design. The first two chapters focus on the joint mechanism and information design by a monopolistic seller. In Chapter 1, facing a buyer whose valuation depends on the buyer’s type and an unknown component, the seller designs information about the unknown component and any allocation rule. The optimal mechanism features either bunching, screening, or a random mechanism. When the variation of valuations is mainly driven by the buyer’s type, it bunches all types with a single posted price and threshold disclosure. Instead, when the unknown component is the main driver, it offers a menu of posted prices and threshold disclosures. Random allocations can help to handle misreporting off-path, enhancing surplus on both intensive and extensive margins. Contracting ex post or interim is irrelevant in many cases. These findings explain distinct strategies of pricing and information provision adopted across industries and stages of a product’s lifecycle, rationalizing the prevalence of free information in many markets.

Chapter 2 investigates the interaction of buyer's optimism, information design, and price discrimination. The model features a continuum of buyers holding biased and private prior beliefs regarding whether the product fits his need. The seller can provide additional information about the product that helps the buyer privately refine his belief. While neither the diversity in the (biased) priors nor information design suffices to trigger price discrimination, their combination induces the optimal mechanism featuring both information and price discrimination. Moreover, the simultaneous presence of information design and biased priors enhances trade surplus when the product fits the buyer, but causes surplus reduction otherwise.

Chapter 3 considers an auction design problem with private values, where the seller and bidders may enjoy heterogeneous priors about their (possibly correlated) valuations. Each bidder forms an (interim) belief about the others based on his own prior, updated by observing his own value. If the seller faces uncertainty about the bidders’ priors, even if he knows that the bidders’ priors are within any given distance from his, he may find it worst-case optimal to propose a dominant-strategy auction mechanism. This provides a foundation for dominant-strategy mechanisms in auctions with heterogeneous priors.

Chapter 4 studies mechanism design with flexible but costly information acquisition. There is a principal and four or more agents, sharing a common prior over the set of payoff-relevant states. The principal proposes a mechanism to the agents who can then acquire information about the state of the world by privately designing a signal device. As long as it is costless for each agent to acquire a signal that is independent of the state, there exists a mechanism which allows the principal to implement any social choice rule at zero information acquisition cost to the agents. Two applications are considered, including auctions with common value and collective.