Since 2007, the European Union consists of 27 member states which face very different challenges with regard to irregular migration. Securing the borders and preventing irregular migration is perceived increasingly as a European policy issue. Visa policy, border protection, return enforcement and measures to reduce incentives for irregular migration are increasingly Europeanized. However, the size and structure of irregular resident populations still depends mainly on national conditions in a large number of fields.
CLANDESTINO Policy Brief on the Size of Irregular Migration (October 2009)