In other words, how powerful is modern day Russia in comparison to the USSR? How many fewer resources does it have now than it did, say, in the 1980s?
Population is easy enough to figure out. Assuming that Wikipedia's figures for the 1989 Soviet census are accurate, the USSR had a population of 286,717,000, while the Russian SSR had a population of 147,386,000 - 51% of the USSR's population.