In 2004, 75 million people across ten countries joined the European Union (EU). Between 2004 and 2019, their GDP per capita doubled. Empirically, I show the new members’ GDP per capita was 32% higher in 2019 thanks to EU accession. I do not find a significant effect on the pre-2004 members. These findings are robust to a wide range of tests. Standard growth accounting indicates that the Solow residual was the primary driver of growth. I interpret these results through a neoclassical growth model with heterogeneous firms facing idiosyncratic distortions. I quantify changes in the joint distribution of productivities and wedges. This wedge accounting exercise implies modest changes in allocative efficiency and substantial improvements in firm-level productivity, consistent with EU accession shifting the technology frontier. These results indicate that, to account for this economic miracle, allowing for technological change is fundamental.