We develop an equilibrium model of industrial structure in which the organization of firms is endogenous. Differentiated consumer products can be produced either by vertically integrated firms or by pairs of specialized companies. Production of each variety of consumer good requires a unique,...

We develop a model of common agency with complete information and general preferences with non-transferable utility, and prove that the principals'Nash equilibrium in truthful strategies implements an efficient action. We apply this theory to construct a positive model of public finance, where...