Historians will look back on this period with awe and wonder. Somehow, three generations of economists and policy-makers have convinced themselves of things that can’t be true. “Not enough demand,” they say, in penetrating analysis of today’s lackluster economic growth rates. “We need to provide demand,” they add, as though demand were like oranges. You just pack up the truck in Florida and deliver them to New York. Easy Peasy. But it almost seems as though the world were created just so its creator could have a good laugh at simpleminded economists.