We consider a general equilibrium model under imperfect competition. Firms have constantreturns, they are price taker in the input market and compete à la Cournot in theproduct market. We assume a representative consumer exists. We show that an increase inthe number of firms of a given market...

This paper presents another definition of substitutes and complements. It follows a dual approach using the Luenberger's benefit function. The benefit function measures the amount of a reference bundle that an individual would be willing to give up to move from a given utility level to any...