We investigate the implications of relaxing Arrow's independence of irrelevant alternatives axiom while retaining transitivity and the Pareto condition. Even a small relaxation opens a floodgate of possibilities for nondictatorial and efficient social choice.

For social choice rules that can select either one or two alternatives, strategy-proofness is incompatible with a weak Condorcet principle.

We examine the extent to which migration equilibria fail to exist in a global economy in which a specific division rule determines the allocation of a perfectly divisible, nondisposable resource among individuals with single-peaked preferences who reside in local economies. In particular, almost...