Quality Competition and a Demand Spillover Effect: A Case of Product Differentiated Duopoly

Employing the price-quality competition model in a horizontally differentiated products market, we analyze how a demand spillover effect associated with upgrading the quality level of a product affects the strategic relationship between firms and the property of a subgame perfect Nash equilibrium. In particular, we show that the strategic relationship depends on the degree of a demand spillover effect. Then, we consider the cases of second-best policy and cooperative quality choice. Furthermore, we illustrate that there exists a natural Stackelberg equilibrium under asymmetric demand spillover effects that is Pareto superior to other equilibria. Finally, we examine an optimal policy with international R&D rivalry.