Empirical Modeling of Policy Diffusion in Federal States: The Dyadic Approach

Abstract

Policy diffusion is a common phenomenon in federal states: indeed, one of the normative justifications of decentralized policy making is that it permits the development and spread of best practices. Following Berry and Berry (1990), event‐history analysis has been the method of choice for the quantitative investigation of policy diffusion, but Volden (2006) has recently introduced a dyadic variant of this method in which units of analysis are not states but, instead, pairs of states. This article discusses the dyadic approach with a particular focus on the diffusion of policies in Switzerland. The goal is not to introduce a new method, but rather to provide a practical overview for researchers interested in using it. The article shows how the method has migrated from the international relations literature to the policy‐diffusion literature, describes the typical structure of a dyadic dataset in a diffusion context, and discusses several modeling issues. The usefulness of the dyadic approach is illustrated empirically with the example of health‐insurance subsidy policies in Swiss cantons.