Auction Design without Commitment

We study auction design when parties cannot commit themselves to the mechanism. The seller may change the rules of the game and the buyers choose their outside option at all stages. We assume that the seller has a leading role in equilibrium selection at any stage of the game. Stationary equilibria are characterized in the language of vonNeumann-Morgenstern stable sets. This simplifies the analysis remarkably. In the one buyer case, we obtain the Coase conjecture: the buyer obtains all the surplus and efficiency is reached. However, in the multiple buyer case the seller can achieve more: she is able to commit to the English auction. Typically the converse also holds, the English auction is the only stable auction mechanism.Auction theory, commitment, stable sets

Extended Conversations in Sender-Receiver Games

Aumann and Hart (Econometrica, Nov. 2003) have shown that in games of one-sided incomplete information, the set of equilibrium outcomes achievable can be expanded considerably if the players are allowed to communicate without exogenous time limits and completely characterise the equilibria from such communication. Their research provokes (at least) four questions. (i) Is it true that the set of equilibriumpayoffs stabilises (i.e. remains unchanged) if there are sufficiently many rounds of communication? (ii) Is the set of equilibria from communication which is unbounded but finite with probability one is the same as equilibria from communication which is just unbounded? (iii) Are any of these sets of equilibria “simple” and if so, is there an algorithm to compute them? (iv) Does unbounded communication (of order type w) exhaust all possibilities so that further communication is irrelevant? We show that in the context of finite Sender-Receiver games, the answer to all four is yes if the game satisfies a certain geometric condition. We then relate this condition to some geometric facts about the notion of bi-convexity and argue that if any of the questions has a negative answer then all three of the questions are likely to have a negative answer.

Veto Players and Policy Trade-Offs- An Intertemporal Approach to Study the Effects of Political Institutions on Policy

The capacity to sustain policies over time and the capacity to adjust policies in the face of changing circumstances are two desirable properties of policymaking systems. The veto player approach has suggested that polities with more veto players will have the capacity to sustain policies at the expense of the ability to change policy when necessary. This paper disputes that assertion from an intertemporal perspective, drawing from transaction cost economics and repeated game theory and showing that some countries might have both more credibility and more adaptability than others. More generally, the paper argues that, when studying the effects of political institutions on policy outcomes, a perspective of intertemporal politics might lead to predictions different from those emanating from more a-temporal approaches.Political institutions, Public policies, Veto players, Policy adaptability, Policy stability, Intertemporal, Credibility, Repeated games