We extend the analysis carried out by Valletti (2000) by considering an environmental externality in a vertically differentiated duopoly where firms compete à la Cournot with fixed costs of quality improvement. We show that, if the weight of the external effect is high enough, the resulting...

We develop a model of vertical innovation in which firms incur a market entry cost and position themselves in the quality space. Once established, firms compete monopolistically in the quality space, selling to consumers with heterogeneous tastes for quality. Exogenously growing productivities...