Overlapping Coalitions, Bargaining and Networks

This paper extends the theory of endogenous coalition formation, with complete information and transferable utility, to the overlapping case. We propose a cover function bargaining game which allows the formation of overlapping coalitions at equilibrium. We show the existence of subgame perfect equilibrium and provide an algorithm to compute this equilibrium in the symmetric case. As an application, we establish an interesting link with the formation of networks.Overlapping Coalitions, Cover Function, Bargaining, Symmetric Game, Network

Incomplete Information and Small Cores in Matching Markets

We study Bayesian Nash equilibria of stable mechanisms in centralized matching markets under incomplete information. We show that truth-telling is a Bayesian Nash equilibrium of the revelation game induced by a common belief and a stable mechanism if and only if all the profiles in the support of the common belief have singleton cores. Our result matches the observations of Roth and Peranson (1999) in the National Resident Matching Program (NRMP) in the United States: (i) the cores of the profiles submitted to the clearinghouse are small and (ii) while truth-telling is not a dominant strategy most participants of the NRMP truthfully reveal their preferences.Matching Market, Incomplete Information, Small Core

Arrow's Theorem for One-Dimensional Single-Peaked Preferences

In one-dimensional environments with single-peaked preferences we consider social welfare functions satisfying Arrow''s requirements, i.e. weak Pareto and independence of irrelevant alternatives. When the policy space is a one-dimensional continuum such a welfare function is determined by a collection of 2N strictly quasi-concave preferences and a tie-breaking rule. As a corollary we obtain that when the number of voters is odd, simple majority voting is transitive if and only if each voter�s preference is strictly quasi-concave.mathematical economics;

Free Triples, Large Indifference Classes and the Majority Rule

We consider situations in which agents are not able to completely distinguish between all alternatives. Preferences respect individual objective indifferences if any two alternatives are indifferent whenever an agent cannot distinguish between them. We present necessary and sufficient conditions of such a domain of preferences under which majority rule is quasi-transitive and thus Condorcet winners exist for any set of alternatives. Finally, we compare our proposed restrictions with others in the literature, to conclude that they are independent of any previously discussed domain restriction.Quasi-Transitivity