Ex pluribus unum: Integrating the different strands of policy diffusion theory

Abstract

Diffusion processes have recently attracted considerable interest from political scientists, who built on the diffusion literatures in sociology, economics, communication studies, and public policy. This ecumenical approach has been fruitful: it has led to complex and multi-faceted accounts of diffusion processes, which, as scholars have shown, are driven by several distinct diffusion mechanisms, such as learning, competition, and emulation. However, most diffusion accounts lack theoretical coherence. The present article addresses this issue in three steps. First, it reviews the recent diffusion literature in political science and shows that it is characterized by considerable theoretical diversity, which has led to internally incoherent explanations. Second, it puts forward a simple model of policy change that is able to supply a basic but effective common theoretical framework for the various diffusion mechanisms identified in the literature. Third, it discusses the implications of this framework for empirical and theoretical research on diffusion.