General equilibrium theory and increasing returns : an alternative to the survival assumption.

Existence results for equilibria in economies under increasing returns to scale, fixed costs, or showing more general types of non convexity in the production sector, strongly rest on a crucial condition, known as the survival assumption. This assumption is unsatisfactory in the sense that it poses a condition on the set of production equilibria, an endogenous variable. We propose here conditions on the firms’ characteristics, notably on the firms' pricing behaviour, under which the equilibrium existence can be proved.