Well, you have to consider the context. The disparity was there even before the Soviet Union existed. The Russian Empire was much poorer (per capita) than Western Europe or the United States. It was significantly behind in industrialization, human development and infrastructure. If fact, the poor state of the Russian economy was one of the reasons Russia did poorly in WWI. When Bolisheviks came to power in 1917, not only was their country already suffering from 3 years of war, they also had to fight for power in the extremely brutal Russian Civil War. Not only that, but hundreds of thousands of people - mostly people of means who were educated and entrepreneurial - left the country to escape persecution. The Soviets did a pretty decent job or rebuilding and catching up in industrialization during the late 1920's and 1930s. However in 1941 the USSR was invaded by Nazi Germany. The war was disastrous for the country, with over 27 million people dead, and huge swath of the country - cities, infrastructure, farmland, etc - almost completely destroyed. Even though the USSR and the allies won in the end, the victory came and an astonishing price. So again the Soviets had to rebuild. Of course none of that excuses poor policy decision and the inefficient nature of a planned economy. However the USSR and the US were never on level playing field. The US never experienced even remotely close to such destruction or casualties from world wars as the Soviet Union did.