We present a nonparametric "revealed-preference test" for gross substitutes in demand for two goods. (JEL D01, D11)

We characterize the structure of the set of core matchings of an assignment game (a two-sided market with transfers). Such a set satisfies a property we call consistency. Consistency of a set of matchings states that, for any matching v, if, for each agent i there exists a matching ? in the set...

We introduce an ordinal model of efficiency measurement. Our primitive is a notion of efficiency that is comparative, but not cardinal or absolute. In this framework, we postulate axioms that an ordinal efficiency measure should satisfy. Primary among these are choice consistency and planning...