In 1989, the Iron Curtain came down, and we could see what a difference it made as we could examine levels of material well-being on both sides of the Curtain. This is as close to a perfect natural experiment as anyone could wish: the Iron Curtain’s location was determined by where Stalin’s and Mao’s and Giap’s armies marched—which is as exogenous to other determinants of economic well-being as anyone could wish.

From How Much Does the Market Organization of Economic Life Matter? - Grasping Reality with Both Hands

Not a perfect match but it does make the case that 50 years of non-market economics leads to 80% to 90% less in economic productivity.