the interest in the competitive model stems partly from its presumed descriptive power and partly from its implications for economic effeciency. in particular , we can state the following well-known proposition (first optimality theorem) . if a competitive equilibrium exists at all , and if all commodities relevant to costs or utilities are in fact priced in the market , then the equilibrium is necessarily optimal in the following precise sense (due to v. pareto) : there is no other allocation of resources to services which will make all participants in the market better off.