Innovation Diffusion in Heterogeneous Populations

New products and practices take time to diffuse, a fact that is often attributed to some form of heterogeneity among potential adopters. People may realize different benefits and costs from the innovation, or have different beliefs about its benefits and costs, hear about it at different times, or delay in acting on their information. This paper analyzes the dynamics arising from different sources of heterogeneity in a completely general setting without placing parametric restrictions on the distribution of the relevant characteristics. The structure of the dynamics, especially the pattern of acceleration, depends importantly on which type of heterogeneity is driving the process. These differences are sufficiently marked that they provide a potential tool for discriminating empirically among diffusion mechanisms. The results have potential application to marketing, technological change, fads, and epidemics. JEL Classification: O33, D8, M3.