Adding Social Structure to Diffusion Models

Most diffusion models make the implausible assumption that diffusion is unstructured by relationships within the population of interest. This article proposes methods for incorporating a priori notions about social structure into analysis. Diffusion is modeled within an event history framework where the individual's rate of adoption is a function of prior adoptions by related actors. Two diffusion models are suggested: an epidemic model where adoption rates vary with the number of prior adoptions, and a salience model where adoption rates vary with time since the last event. This approach is illustrated in an examination of the decolonization of British and French colonies. Diffusion is shown to occur within regions rather than within empires or the world system as a whole.