[This paper gives a constructive existence proof of a general equilibrium for a local public goods economy in which consumers are free to move among regions. The proof is based upon the Scarf algorithm for the computation of fixed points.]

[A choice function C on X identifies, for each subset Y of X, a set C(Y) of "best" alternatives in Y. A. computationally viable choice function is one for which a member of the choice set C(Y) can be located by a computational procedure which does not waste time, generates reasonably satisfactory intermediate alternatives, and adjusts easily as new alternatives become available. Computational viability is defined precisely and the class of computationally viable choice functions is neatly characterized. In addition, the various types of binary choice functions are distinguished in terms of computational criteria.]

It is known that the price mechanism whereby the rate of change of a price is proportional to the excess demand of the corresponding commodity need not converge to a competitive equilibrium for a pure exchange economy with more than two commodities. On the other hand, there exist convergent price mechanisms, similar to the Newton iterative process, where the rate of change of the prices is determined by the excess demand and the marginal excess demands of all the commodities. This is a considerable informational requirement. It is shown that this requirement cannot be substantially reduced for any convergent price mechanisms, that is for price mechanisms expressed in terms of a difference or differential equation where the solutions converge to a competitive equilibrium.