“It seems an extraordinary imbecility that this wonderful outburst of productive energy should be the prelude to impoverishment and depression,” Keynes wrote in 1931, after the boom years of the 1920s had given way to the Great Depression. “I find the explanation of the current business losses, of the reduction in output, and of the unemployment which necessarily ensues on this not in the high level of investment which was proceeding up to the spring of 1929, but in the subsequent cessation of this investment.”
在许多经济学家看来，衰退是经济周期不可避免的一部分——无论任何繁荣，随后的爆破是必然的，就像痛饮之后的宿醉。然而约翰·梅纳德·凯恩斯（John Maynard Keynes）并不认同这一观点，“将生产能力的巨大膨胀视为贫困和衰退的必然前奏是非常愚蠢的，”凯恩斯在1920年代经济繁荣转向大萧条后的1931年写到。“我发现当前商业亏损，产量减少及高失业率并非源自于一直延续到1929年春天的高投资水平，而是因为随后出现的投资中断。”