[The core is the set of all unblocked allocations. Implicit in this definition is the idea that if an allocation is proposed which could be blocked, some coalition will form and issue a counterproposal which it can enforce. A process of successive counterproposals based on this idea is shown to converge in a finite period of time (amost surely) to the core.]

[The existence of an equilibrium is proven for a two-period model in which there are spot transactions and futures transactions in the first period and spot markets in the second period. Prices at that date are viewed with subjective uncertainty by all traders. This introduces the possibility of speculation. Conditions for the existence of a competitive equilibrium include restriction on the nature of price expectations.]

This paper is concerned with tax policies designed to obtain an improved competitive allocation in the presence of consumption externalities. It is known that the full optimum can, in general, be attained only through the imposition of excise taxes at different levels for different individuals. Since these may be ruled out (possibly because of implementation costs), one is confined to consider second-best taxes. The common interpretation of the Pigouvian principle has called for taxes on the externality-creating commodities. With no relationships between the consumption of different commodities the Pigouvian principle is obviously impeccable. But the existence of substitutes or complements for an externality-causing commodity raises the possibility of indirect policies: treating the externality through the markets for related goods. Obviously, if the direct policy is not feasible, the indirect treatment may provide some partial remedy. We show, however, that even when direct policies are available, the overall optimum may involve only indirect policies. An example with such a result is provided in the paper. We also list a number of cases in which the traditional prescription is confirmed, and the overall optimum involves only direct policies.

I. Introduction, 138. — II. Outline of Arrow's model and results, 138. — III. Public goods, 139. — IV. Expenditures as produced commodities, 140. — V. Examples, 142. — VI. Conclusion, 144.

This paper formulates the notion of stochastic equilibria as invariant probability distributions consistent with the behavior patterns of individuals and the disequilibrium adjustment mechanism of the economy. Conditions for existence, uniqueness, and stability of such equilibria are examined. WE CONSIDER A CLASS of problems in this paper in which the economic environment is stochastic. We will be concerned primarily with developing an equilibrium concept for general equilibrium models of this type. However the essential ideas can be carried over directly to partial equilibrium applications. The choice of the specific general equilibrium model used results primarily from a desire to facilitate comparisons with earlier work on alternative equilibrium concepts for this model (see Hildenbrand [9] and Majumdar and Bhattacharya [2 and 3]). Randomness can arise from several sources. We will be considering, for concreteness, a simple exchange economy in which the basic data are the preferences and endowments of the economic agents. Either of these can be random. Typically, randomness of endowments can be allowed for by creating contingent markets in which case the Arrow-Debreu deterministic equilibrium suffices. It is conceptually much more difficult to create markets contingent on tastes due to the difficulties of discovering the true taste pattern of an individual, difficulties which do not arise in the case of endowment vectors which can be observed directly. We will be considering an economy without markets for every future contingency and thus there will remain some randomness. This residual uncertainty in the economy necessitates equilibrium concepts other than the Arrow-Debreu system of market clearing prices. 2. NOTATION

In a principal-agent model with adverse selection, we study the implementation of social choice functions when the agent's message space is a correspondence which depends on this true characteristic. We characterize such correspondence for which the Revelation Principle is valid.

Journal Article The Non-existence of Informational Equilibria Get access Jerry Green Jerry Green Harvard University Search for other works by this author on: Oxford Academic Google Scholar The Review of Economic Studies, Volume 44, Issue 3, October 1977, Pages 451–463, https://doi.org/10.2307/2296901 Published: 01 October 1977 Article history Received: 01 April 1975 Accepted: 01 October 1976 Published: 01 October 1977

An individual with known preferences over lotteries can be led to accept random wealth distributions different from his initial endowment by a sequential process in which some uncertainty is resolved and he is offered a new lottery in place of the remaining uncertainty. This paper examines the restrictions that can be placed on an individual's preferences by axioms that stipulate that such a process not be able to generate a new wealth distribution that is prima facie inferior to the original. The relationship of these axioms to the independence axiom of von Neumann and Morgenstern and to the quasi convexity of preferences in the wealth distribution are explored.