Migrations from Poland since accession to the European Union
Since Poland's accession to the European Union in 2004, migration to and from the country has been in flux. Following accession to the Schengen Area in particular, a significant number of Poles, estimated at over two million, have emigrated, primarily to the United Kingdom, Germany, France and Ireland.
Source: Wikipedia — Migrations from Poland since accession to the European Union (CC BY-SA 4.0)