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 absence of simultaneous cycles is a sufficient condition for the existence of singleton cores. Acyclicity in the preferences of either side of the market is a minimal condition that guarantees the existence of singleton cores.

In social choice settings with linear preferences, random dictatorship is known to be the only social decision scheme satisfying strategyproofness and ex post efficiency. When also allowing indifferences, random serial dictatorship (RSD) is a well-known generalization of random dictatorship that...

In this paper, virtual implementation is restricted to deliver, on the equilibrium path, either a socially optimal outcome or a status quo: an outcome fixed for all preference profiles. Under such a restriction, for any unanimous and implementable social choice function there is a dictator, who...

In the problem of allocating workers to different projects, where each project needs a minimum number of workers assigned to it, the serial dictatorship mechanism is neither strategy proof nor Pareto efficient. We therefore propose a strategy-proof and Pareto-efficient mechanism.

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...

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...

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.

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.

Recent research on the Condorcet Jury Theorem has proven that informative voting (that is, voting according to one’s signal) is not necessarily rational. With two alternatives, rational voting typically leads to the election of the correct alternative, in spite of the fact that not all voters...