I might have heard it before, but it evidently didn’t keep since I was so surprised to see Dan Drezner’s graphs. They both have pretty flat trajectories in the 50s, then begin to improve in the 60s, but while South Korea continues to accelerate upward the North flatlines and then regresses. How did other communist nations compare? I know Charles Kenny* has argued even now in hindsight it wasn’t an obviously inferior economic system (though certainly brutal to its citizens). Note that he is comparing to the global average rather than first world, since much of the world did terribly under that time period.