Gorkem Celik

Mechanism Design with Collusive Supervision

We analyze an adverse selection environment with third party supervision. The supervisor is partly informed of the agents type. The supervisor and the agent collude while interacting with the principal. Contracting with the agent directly and ignoring the presence of the supervisor constitutes the no-supervision benchmark. We show that delegating to the supervisor reduces the principals payoff compared to the no-supervision benchmark under a standard condition on the distribution of the agents types. In contrast, if the principal contracts with both the agent and the supervisor, there exists a mechanism that improves the principals payoff over the no-supervision payoff.

Optimal Auctions with Simultaneous and Costly Participation

We study the optimal auction problem with participation costs in the symmetric independent private values setting, where bidders know their valuations when they make independent participation decisions. After characterizing the optimal auction in terms of participation cutoffs, we provide an example where it is asymmetric. We then investigate when the optimal auction will be symmetric/asymmetric and the nature of possible asymmetries. We also show that, under some conditions, the seller obtains her maximal profit in an (asymmetric) equilibrium of an anonymous second price auction. In general, the seller can also use non-anonymous auctions that resemble the ones that are actually observed in practice.

Mechanism design with weaker incentive compatibility constraints

We study an adverse selection problem, where an agent is able to understate his productivity, but not allowed to overstate it. The solution to this problem is generally different than the solution to the standard problem, where no restriction is made on the statements of the agent. We identify a sufficient condition, that does not depend on the distribution of types, under which these two solutions coincide.

Equilibrium rejection of a mechanism

We study a mechanism design problem in which players can take part in a mechanism to coordinate their actions in a default game. By refusing to participate in the mechanism, a player can revert to playing the default game non-cooperatively. We show with an example that some allocation rules are implementable only with mechanisms which will be rejected on the equilibrium path. In our construction, a refusal to participate conveys information about the types of the players. This information causes the default game to be played under different beliefs, and more importantly under different higher order beliefs, than the interim ones. We find a lower bound on all the implementable payoffs. We use this bound to establish a condition on the default game under which all the implementable outcomes are truthfully implementable, without the need to induce rejection of the mechanism.

Reciprocal Relationships and Mechanism Design

We study an incomplete information game in which players are involved in a reciprocal relationship that allows them to coordinate their actions by contracting among themselves. We model this as a competing mechanism game in which players have the ability to write contracts. We characterize the set of outcome functions that can be supported as equilibrium in this enhanced game. We use our characterization to show that the set of supportable outcomes is bigger than the set of outcomes supported by a centralized mechanism designer who can offer mechanisms in which all players participate. The difference is that the contracting game makes it possible for players to convey partial information about their type at the time they offer contracts.