Around 6 million Polish citizens perished during World War II: about one fifth of the pre-war population. Most were civilian victims of the war crimes and crimes against humanity during the occupation by Nazi Germany and the Soviet Union. Statistics for Polish World War II casualties are divergent and contradictory. This article provides a summarization of these estimates of Poland's human losses in the war and their causes. The official Polish government report on war damages prepared in 1947 put Poland's war dead at 6,028,000; 3.0 million ethnic Poles and 3.0 million Jews not including losses of Polish citizens from the Ukrainian and Belarusian ethnic groups. This figure was disputed when the communist system collapsed by the Polish historian Czesław Łuczak who put total losses at 6.0 million; 3.0 million Jews, 2.0 million ethnic Poles, and 1.0 million Polish citizens from the other ethnic groups not included in the 1947 report on war damages. In 2009 the Polish government-affiliated Institute of National Remembrance (IPN) published the study "Polska 1939–1945. Straty osobowe i ofiary represji pod dwiema okupacjami" (Poland 1939-1945. Human Losses and Victims of Repression Under the Two Occupations) that estimated Poland's war dead at between 5.6 and 5.8 million Poles and Jews, including 150,000 during the Soviet occupation. Poland's losses by geographic area include about 3.5 million within the borders of present-day Poland, and about two million in the Polish areas annexed by the Soviet Union. Contemporary Russian sources include Poland's losses in the Polish areas annexed by the Soviet Union with Soviet war dead. In Poland this is viewed as inflating Soviet casualties at Poland's expense.