The dynamics of innovation and horizontal differentiation

We study innovation in a dynamic stochastic discrete-time duopoly with endogenous horizontal differentiation. Innovation takes the form of a quality ladder; horizontal differentiation is Hotelling competition. We compute Markov-perfect equilibria and study the effects on long-run innovation of changes in taste heterogeneity (transport costs) and firms' costs of relocating products. Innovation rises as the industry's long-run position moves toward products that are permanently co-located in the space of horizontal tastes. A large enough fall in taste heterogeneity will raise long-run innovation, while more costly product relocation lowers innovation if taste heterogeneity is high, and raises it otherwise.