We discuss how efficiently a unit tax deals with external damage problems when economies of scale characterize a monopolistically competitive market in which consumers' value product variety. It turns out that neither the number of varieties nor the quantity of each variety is at the optimum...

In a two-stage Cournot oligopoly cost minimization sometimes calls for ex ante identical firms to invest in diverse technologies. It is an implication of this result that it might be optimal to treat identical duopolistic polluters asymmetrically. We discuss the efficiency properties of a...