The developments in economic theory in the 1950s served to pinpoint important underlying assumptions in the study of market institutions. The conflict between observed institutions - spot markets for commodities, financial markets - and the benchmark interpretation - forward markets for commodities, allowing all trade to take place at a single point in time, became apparent. This led to the introduction of new equilibrium concepts; temporary equilibria, spot-market equilibria and monetary equilibria. The emphasis was on the possibilities to transfer purchasing power over time or over states using spot markets involving assets or money. This book focuses on the developments in the theory of incomplete markets and overlapping generations economies where income transfers over time or across states are restricted either by available assets or by the infeasibility of contracts with unborn generations. It bridges the gap between standard textbooks on microeconomics and more advanced expositions.

Modern welfare economics as it is known today to economists took its final shape with the emergence of the Arrow-Debreu model. The classical conjectures about the beneficient workings of markets together with the converse statement, that optimal (in the sense of Pareto) allocations may be sustained by prices and markets, has laid a firm foundation for further research in welfare economics. But more than that, it has inspired researchers to take up entirely new topics, notably by closer considerations of situations where the assumptions of the original model may seem overly restrictive. One of these new directions has been connected with generalizing the model so that it takes into account the possibility of infinitely many commodities. On the face of it, the idea of an infinity of commodities may seem a mathematical fancy having no "real" counterpart in economic life. This is not so, however. Quite to the contrary, infinity enters in a very natural way when it is taken into account that economic transactions take place over time. 2 In the Arrow-Debreu formalism, time may be incorporated into the model in a very simple way using dated commodities. Thus two commodities are considered as being different if they are to be delivered at different points of time.

The developments of economic theory in the 1950s served to pinpoint important underlying assumptions in the study of market institutions. The conflict between observed institutions and the benchmark interpretation became apparent. This led to the introduction of new equilibrium concepts. The emphasis was on the possibilities to transfer purchasing power over time using spot markets involving assets or money. This advanced textbook focuses on the developments in the theory of incomplete markets and overlapping generations economies where income transfers over time are restricted either by available assets or by the unfeasibility of contracts with unborn generations. It bridges the gap between standard textbooks on microeconomics and more advanced expositions. Contains diagrams, examples and exercises.