Attitudes of national decision-makers towards differentiated integration in the European Union

Differentiated integration (DI) in the European Union (EU) has mainly been understood as variation in participation in common policies. But DI also has implications for the nature and functioning of the EU as a polity. While temporary DI may facilitate deeper integration, permanent DI is liable to increase transaction costs and fragmentation. However, little is known about how such alternatives are assessed by decision-makers in the member states. This article uses novel quantitative and qualitative data to shed light on this question. It looks at the explanatory role of various types of opt-outs and at member states’ dependence, capacity, and identity. We find that temporary and permanent differentiation are assessed differently in the member states but neither alternative is clearly preferred. Long-term involuntary opt-outs are related to negative assessments of both forms of DI. Surprisingly, voluntary opt-outs do not seem to lead to more positive assessments of DI. We also find that the temporary DI is preferred in smaller member states, while support for permanent DI is higher in larger member states. Finally, we find differences in the effects of dependency, capacity, and identity between older and newer member states.