A Quantitative Analysis of Legal Integration and Differentiation in the European Union, 1958-2020

The article provides an innovative, comprehensive quantitative analysis of legal integration and differentiation in the European Union (EU) from 1958 to 2020. Building on a streamlined analytical framework and new or revised datasets on EU primary, EU secondary and EU-related international law, it challenges or qualifies several aspects of the received wisdom on European integration. Specifically, it delivers the first-ever quantitative estimate of integration in terms of integration opportunities, shows that differentiation is deployed in a reluctant and eclectic manner and offers clear measurements for the prevalence of various modes of temporal, spatial and policy differentiation. These methodological and empirical findings confirm the fruitfulness of the quantitative approach to the study of European integration and point to promising avenues for future research on international integration and comparative regionalism.