It is shown that any informationally decentralized mechanism that realizes fair allocations over the class of classical pure exchange environments has a message space of dimension no smaller than the number of agents times the number of commodities. Since the equal income Walrasian mechanism, in which all agents take prices parametrically and maximize utility subject to the average income constraint, realizes fair outcomes over the class of classical pure exchange environments and has a message space of that dimension it is informationally efficient. Further, it is shown that it is the unique informationally efficient mechanism realizing fair allocations.

This paper develops a dynamic model of oligopoly and discusses the existence and characteristics of optimal policies for firms in such a model. The firms are assumed to face a random demand so they hold inventories which fluctuate from one period to the next. This necessitates a dynamic model rather than a static one. Our extension of the equilibrium concept to the oligopoly model is founded on recent generalizations of Shapley's stochastic game. We show the existence of equilibrium price-quantity strategies for the firms and also (i) an equilibrium strategy may be found by solving an appropriate static game and (ii) the quantity part of the strategy is often a constant (time invariant).