⁴Because of the limited inter-regional migration data provided by Eurostat (especially for Greece and Spain) this analysis follows the approach used by Crescenzi, Rodríguez-Pose (2008) and Puhani (2001) in order to calculate the net migration rate. The data on net migration is calculated as the population change plus deaths minus births. “The net migration data retrieved in this way also includes external migration” (Puhani 2001, 132). Moreover, we standardize the net migration by the average regional population. “Consequently, it is impossible to distinguish between national, intra-EU and extra-EU migration flows” (Crescenzi, Rodríguez-Pose 2008, 72).