1948, dictated the dominant direction of Poland's future foreign trade and economic cooperation. In 1948, the United States announced the Marshall Plan initiative to help rebuild postwar Europe and thus gain more political power there. After initially welcoming the idea of Poland's participation in the plan, the Polish government declined the American offer under pressure from Moscow. Also, following the Uprising of 1953 in East Germany, Poland was forced by the Soviet Union to give up its claims to compensation from Germany, which as a result paid no significant compensation for war damages, either to the Polish state or to Polish citizens. Poland received compensation in the form of land and property left behind by the German population of the annexed western territories. Despite the lack of American aid, the East European "command economies", including Poland, made some progress in bridging the historically existing wealth gap with the market economy driven Western Europe. Because of the capital accumulation, the Polish national income grew in real terms by over 76% and the agricultural and industrial production more than doubled between 1947 and 1950. The economic transition and industrialization were accompanied and made possible by massive social transformations, as peasants migrated and were converted into city dwelling working class (1.8 million between 1946 and 1955) and the country went through a period of rapid urbanization (total population of the cities increased by 3.1 million). The influx of cheap labor and the availability of the Soviet market facilitated an accumulation of resources, despite low productivity and insufficient investment in new technologies. The centrally planned socialist economies of Eastern Europe in terms of growth during the postwar years did relatively better than the West, only to sustain economic damage later, especially after the 1973 oil crisis. However, the rise in living standards caused by the earlier industrial dynamics was not comparable to that in the West. Reforms, resistance and beginning of de-Stalinization The last Polish–Soviet territorial exchange took place in 1951. Some of land along the border were swapped between Poland and the Soviet Union. The Constitution of the Polish People's Republic was promulgated in July 1952 and the state officially became the Polish People's Republic (PRL). Among the rights it guaranteed was universal free health care. The large state-owned enterprises provided to employees an extensive range of welfare and leisure activities, including housing, sports facilities and hospitals, which started to diminish in the