The European Single Market and Intra-EU Trade: An Assessment with Heterogeneity-Robust Difference-in-Differences Methods

We use heterogeneity-robust difference-in-differences (DiD) methods to evaluate the impact of membership in the European Union (EU) Single Market on international trade. On the policy front, we provide evidence that: (i) On average, the EU has been very effective in promoting trade among its member states; (ii) The trade effects of the EU have been long-lasting, but heterogeneous across EU cohorts; and (iii) While the EU has benefited both ‘old’ and ‘new’ members, the increase in the exports from the ‘old’ members to the ‘new’ joiners has been disproportionately larger. From a methods and practical perspective, the contribution of this paper is to introduce a new, fast, and flexible estimation command that combines leading estimation techniques from the gravity literature with recent methods from the heterogeneity-robust DiD literature.