sentences:  In 2007, Chorzów became a part of Upper Silesian Metropolitan Union, a voluntary union of a continuous chain of cities aimed at increasing the poor visibility of the area, improving its competitiveness, and modernizing the infrastructure.The region experienced several waves of migrations, including those commencing in 1945 (to Germany and from Poland and Ukraine), in 1971–1976 (to Germany), in 1982 (to Western countries), and from 2003 (to other countries of the EU).Chorzów is in the middle of the largest urban center in Poland.