… is from page 134 of Deirdre McCloskey’s 2010 Bourgeois Dignity :
During the 1930s and early 1940s the prospect of diminishing returns deeply alarmed economists such as the British economist John Maynard Keynes and the American follower of Keynes at Minnesota and Harvard, Alvin Hansen. They believed that the technology of electricity and the automobile were exhausted, and that sharply diminishing returns to capital were at hand, especially in view of declining birthrates. People would save more than could be profitably invested, the “stagnationists” believed, and the advanced economies would fall into chronic unemployment. In line with the usual if doubtful claim that spending on the war had temporarily saved the nonbombed part of the world’s economy, they believed that 1946 would see a renewal of the Great Depression.
But it didn’t. Stagnationism proved false.