The Diffusion of Policy Diffusion Research

Within the past decade, more than four hundred articles on policy diffusion have been published in political science journals. These articles have been spread fairly evenly across the subfields of American politics, comparative politics, and international relations. Analyzing the diffusion articles published in the top political science journals over the past fifty years, we find that the American politics subfield is the most tightly focused, that comparative politics scholars draw to the greatest extent on other subfields, and that international relations and comparative politics have a significant degree of overlapping works. Although policy diffusion studies are on the rise in all three subfields, much more can be learned from one another. Having surveyed the literature, we address the who, what, when, where, how, and why of policy diffusion in order to identify and assess some of the main findings of the current scholarship, remaining holes, and paths forward. In addition, we argue that this literature could benefit from a more systematic approach to tackling the questions of when and how policy diffusion takes place, and of why diffusion studies are important to a better understanding of politics. * Preliminary draft – questions and comments are welcomed. The authors thank Rachel Schneider for valuable research assistance, Derek Stafford for helpful assistance with network analyses, and participants at the 2008 Annual Meetings of the American Political Science Association for useful suggestions. 1 The Diffusion of Policy Diffusion Research Over the past half century, political science journals have published nearly 800 articles about the politics of public policies spreading from one government to another, a phenomenon commonly referred to as “policy diffusion.” More than half of these articles have been published in the past decade, indicating a dramatic surge in interest in diffusion. We believe that it is time to pause and take stock in where we have come from, where we currently are, and where we could and should be going in future scholarship. Although such reviews and assessments have been made from time to time within the subfields of political science (e.g., Bennett 1991; Karch 2007; Simmons, Dobbin, and Garrett 2006; Stone 1999), our goal here is to look within and across subfields in order to provide a more complete overview of the literature and to integrate the insights of multiple fields. Examples of the usefulness of integration are plentiful. In the case of international relations (IR), trends beginning in the late twentieth century and continuing into the twenty-first include the rise of globalization where power and information are increasingly decentralized and where barriers to the exchange of ideas, information, and resources are in decline. Simultaneously, however, we see nations turning increasingly to centralized, regional bodies (e.g., the EU, AU, and ASEAN) to handle interstate affairs (Milner and Mansfield 1999). These trends point toward the increasing relevance of questions related to the potential benefits of devolution versus centralization, longstanding issues confronted by policy diffusion scholars studying American federalism. As IR scholars turn toward these questions (e.g., Vogel 1995; Prakash and Potoski 2006; Prakash and Kollman 2003; Zeng and Eastin 2007) they will benefit from communication with earlier diffusion scholarship in the domestic realm.