Innovation Diffusion in Heterogeneous Populations.

New ideas, products, and practices take time to diffuse, a fact that is often attributed to some form of heterogeneity among potential adopters. This paper examines three broad classes of diffusion models -- contagion, social influence, and social learning – and shows how to incorporate heterogeneity into each at a high level of generality without losing analytical tractability. Each type of model leaves a characteristic ‘footprint’ on the shape of the adoption curve that provides a basis for discriminating empirically between them. The approach is illustrated using the classic study of Ryan and Gross on the diffusion of hybrid corn