Abstract This study evaluates the evolution of economic integration within the European Union’s Single Internal Market by developing four de facto indicators that measure the realised intensity of the free movement of goods, services, capital and active population. Using harmonised data for all EU-27 Member States from 1995 to 2020, each indicator is constructed as the normalised average of inward and outward flows relative to GDP or total active population. Data gaps were addressed through controlled interpolation, while cross-source harmonisation ensured conceptual consistency. Integration increased substantially across all freedoms, but unevenly. Goods trade grew by about 50%, led by Central-Eastern European economies embedded in EU value chains. Services trade nearly doubled, dominated by small open economies. Capital integration rose most sharply (≈ 580%) due to financial-hub dynamics. Labour mobility expanded by over 200% but showed core–periphery patterns and a marked 2020 decline due to COVID-19 restrictions. GIS-based exploratory spatial data analysis, including Global Moran’s I and Local Indicators of Spatial Association (LISA), was employed to assess spatial autocorrelation and identify high-integration clusters. This analysis reveals distinct geographic logics for each market freedom. Goods integration forms a strong Central-European manufacturing corridor, characterised by high-high clusters of countries embedded in cross-border value chains. Services and FDI integration, in contrast, are concentrated in spatially isolated hubs such as Luxembourg, Malta, Cyprus and the Netherlands, reflecting their specialised economic and regulatory environments. Labour mobility exhibits a pronounced east–west core–periphery structure, with sending and receiving regions clearly identified through LISA clustering. Overall, the results show substantial long-term deepening of the Single Internal Market but highlight significant and persistent asymmetries across Member States and freedoms. The combination of de facto indicators with spatial analysis provides a more comprehensive understanding of differentiated integration in the EU. The findings underscore the need for targeted policy interventions—particularly in services liberalisation, balanced labour mobility and capital regulation—to support a more cohesive and geographically inclusive trajectory for the Single Market. The analysis is intended as a diagnostic mapping of realised integration patterns rather than a forecasting or policy-effectiveness evaluation framework.
Panayiotis et al. (Mon,) studied this question.