A necessary and sufficient condition for an input to be inferior is that, taking into account the input adjustment, an increase of its price raises the marginal productivity of all inputs. Contrary to a widespread opinion, it is not necessary that (some) inputs are “rivals” (i.e., that some...

We study imperfect and monopolistic competition with asymmetric preferences over a variety of goods provided by heterogeneous firms. We show how to compute equilibria through the Morishima elasticities of substitution. Simple pricing rules and closed-form solutions emerge under monopolistic...