Prior to the Great Depression, opinions about how to properly manage the economy were dominated by Neoclassical economics, which advocated little government intervention. In particular, unemployment was regarded as the consequence of workers failing to accept wages sufficiently low to permit full employment.
During the Great Depression, unemployment soared to 25% in the USA and Germany. Economics had no advice to give to leaders anxious to do something, and none of the neoclassical predictions were coming true. The government of the UK commissioned J.M. Keynes to lead a commission of top British economists in a general review of economic theory; their finding were summarized by Keynes in *The General Theory*.
The Cambridge team did not have access to statistics of national income and product accounting (NIPA). They did have some data on unemployment and prices, especially from the USA.
Keynes also identified several inherent logical problems with neoclassical econo...