According to various estimates, Lviv lost between 80% and 90% of its prewar population. Expulsion of the Polish population and the Holocaust together with migration from Ukrainian-speaking surrounding areas (including forcibly resettled from the territories which, after the war, became part of the Polish People's Republic), from other parts of the Soviet Union, altered the ethnic composition of the city. Immigration from Russia and Russian-speaking regions of Eastern Ukraine was encouraged. The prevalence of the Ukrainian-speaking population has led to the fact that under the conditions of Soviet Russification, Lviv became a major centre of the dissident movement in Ukraine and played a key role in Ukraine's independence in 1991.