The proposition that markets drive economic efficiency is central to much of economics. Adam Smith illustrated that the "invisible hand” of the market drives efficient allocation of resources in a system of division of labor. Friedrich Hayek illustrated the central importance of the price system as an information processing mechanism more powerful than any centrally planned system could ever be. Kenneth Arrow and Gerard Debreu illustrated that complete and perfect markets deliver a Pareto-efficient equilibrium, in which no one person can be made better off without making someone else worse off. And the development of the efficient- market and rational- expectations hypotheses suggested that financial markets are in fact efficient, and that the conditions required for efficiency and for rational and stable equilibria apply even in contracts between the present and the future, which financial markets provide.