Dynamic Product Diversity

The goal of this paper is to study the frequency of new product introductions in monopoly markets where demand is subject to transitory saturation. We focus on those types of goods for which consumers purchase at most one unit of each variety, but repeat purchases in the same product category. The model considers inÖnitely-lived, forward-looking consumers and Örms. We show that the share of potential surplus that a monopolist is able to appropriate increases with the frequency of introduction of new products and the intensity of transitory saturation. If the latter is su¢ ciently strong then the rate of introduction of new products is higher than socially desirable (excessive dynamic product diversity.)