The distinction between nonatomicity and thick markets as the source of perfect competition is examined. The authors construct a model of an imperfectly competitive economy with a nonatomic continuum of traders and a continuum of differentiated commodities for which Walrasian equilibria exist....

The first theorem of welfare economics rests on the assumption that individuals have neither price-making nor market-making capacities. The authors offer a revision in which individuals have such capacities. The revision emphasizes two keys for market efficiency: the need to align private...

Two of the most important refinements of the Nash equilibrium concept for extensive form games are (trembling hand) perfect equilibrium and sequential equilibrium. It is shown here that, for almost all assignments of payoffs to outcomes, the sets of sequential and perfect equilibrium strategy...

The existence of competitive equilibrium is established for economies with a produc tion sector and an infinite dimensional space of commodities. The cru cial assumptions which are required (beyond those required in the fin ite dimensional setting) are bounds on marginal rates of substitution...

This paper proposes a new approach to the study of economic problems that have hitherto been modeled as games with discontinuous payoffs. Typically, the discontinuities arise from indeterminacies in the underlying problem. The authors' point of departure from the conventional approach is to view...