Differentiated Integration in the European Union: Trends and Patterns

Differentiated integration, the selective exemption or exclusion of member states from EU rules and policies, is a central feature of the European Union. In this article, we describe the main trends and patterns of differentiated integration over time, between member states, and across EU policies, based on a unique dataset of differentiation in the EU treaties and legislation. Whereas differentiations have increased in number over time, they have mostly been temporary and served to facilitate the expansion of European integration to new members and policies. Moreover, we observe a current trend of consolidation.