… is from page 103 of John Wallis’s 1993 essay “The Great Depression: Can It Happen Again?” – which is chapter 12 of the knowledge-packed, Deirdre N. McCloskey-edited volume Second Thoughts:
The most important lesson to be learned from the 1930s is that in a crisis it is politics, not economics, that determines what the goals of government policy will be. Politically expedient policy can yield disastrous economic results.