"The other response [to the failure of the Lucas project], by those who had already invested vast effort and their careers in the Lucas project, was to drop the whole original purpose of the project, which was to explain why demand shocks matter. They turned instead to real business cycle models, which asserted that the ups and downs of the economy are caused by technological shocks magnified by rational labor supply responses. Full disclosure: this has always seemed absurd to me; as many have pointed out, the idea that the unemployed during a recession are voluntarily choosing to take time off is something only a professor could believe. But the math was impressive, and RBC became a self-contained, self-replicating intellectual world. [...] The Lesser Depression arrives. It’s clearly not a technological shock; clearly, also, nobody is confused about whether we’re in a slump, as the old Lucas model required."