The first category consists of pairs of destination and origin countries, all form the first group The second category consists of pairs of origin-destination countries, where the destination countries come from the first group and the origin countries come from the seeond group. The third category consists of pairs of destination-origin countries, where the destination countries come from the first group and the origin countries come from the third group This decomposition enables to plausibly assume that migration is free among the 16 EUR countries. Migration is effectively policy-controlled