An alternative is a Condorcet winner if it beats all other alternatives in a pairwise majority vote. A social choice correspondence is a Condorcet extension if it selects the Condorcet winners–and nothing else–whenever a Condorcet winner exists. It is well known that Condorcet extensions are...

In this paper, we give a sufficient condition for double implementation in Nash and M-Nash equilibria. Furthermore, we discuss the mechanism with transfers and prove that some important social choice rules are doubly implemented in Nash and M-Nash equilibria by the mechanism with transfers.

We prove the following result which is equivalent to the Gibbard–Satterthwaite Theorem: when there are at least 3 alternatives, for any unanimous and strategy-proof social choice function, at any given profile if an individual’s top ranked alternative differs from the social choice, then she...

We show that any deterministic mechanism, for allocating identical items that are complements to budget-constrained bidders, cannot simultaneously satisfy individual-rationality, strategy-proofness, Pareto-efficiency, and no-positive-transfers. This holds even for two bidders, two items, and...

This paper is concerned with the problem of extending an antisymmetric binary relation on a set to a linear order on the power set. A necessary and sufficient condition is offered.

We show that every strategy-proof random social choice function is a convex combination of strategy-proof deterministic social choice functions in a two-alternative voting model. This completely characterizes all strategy-proof random social choice functions in this setting.

We study the general problem of public choice. We consider environments where agents’ identities may not be observable. A “rule” associates a preference profile with an alternative. An agent may create fictitious identities and submit multiple preference relations under them. We study...

In a model with finitely many agents who have single-dipped Euclidean preferences on a disc in the Euclidean plane, a rule assigns to each profile of reported dips a point of the disc. It is proved that any strategy-proof and Pareto optimal rule is dictatorial. This framework models situations...

We provide a short proof for the following characterization of the core in housing markets first proved by Ma (1994): the core is the only rule that satisfies strategy-proofness, Pareto efficiency and individual rationality.

The Condorcet rule on the domain of profiles at which there exists a unique Condorcet winner is the unique rule satisfying anonymity, neutrality, and strategy-proofness.