The political science literature lacks a clear distinction of the terms policy-convergence, policy-diffusion and policy-transfer. As a result, there is a considerable amount of terminological and analytical imprecision, impeding a thorough synthesis of the various conceptual and approaches related to these terms and the development of a coherent research program. Against this backdrop, this introductory chapter has two aims. In a first step, the concepts of diffusion, transfer and convergence are defined and systematically related to one another. In a second step, the most important findings from the contributions to this special issue are presented in the context of this overarching framework. Based on the contributions we find that policy convergence, policy diffusion and policy transfer play an important role in international politics and can be encountered in a wide range of policy areas. The main causes and mechanisms underlying these processes are parallel problem pressures, on the one hand, and transnational communication and cross-national policy learning, on the other. Compared to these mechanisms, coercion and conditionality play only a minor role in our case studies. Similarly, the impact of international competition and economic globalisation on domestic policies is surprisingly low. In addition, it seems to be restricted to those policy areas that are directly market-relevant, such as tax policy or labour-market policy.

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