This is a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in economics. - Paul Krugman

So why did spatial issues remain a blind spot for the economic profession? It was not a historical accident: there was something about spatial economics that made it inherently unfriendly terrain for the kind of modeling mainstream economists know how to do. That something was, as you might well guess, the problem of in the face of increasing returns, a problem that is even more acute in than in . In development the crucial role that high assigned to increasing returns was a hypothesis crucial to that doctrine, but not necessarily crucial to understanding development in general. One could do meaningful theorizing about developing countries, albeit not in the grand tradition, without sacrificing the convenient assumptions of constant returns and perfect competition. In spatial economics, however, you really cannot get started at all without finding a way to deal with scale economies and oligopolistic firms.

There are many economic puzzles, but there are only two really great mysteries.
One of these mysteries is why economic growth takes places at different rates over time and across countries. Nobody really knows why the U.S. economy could generate 3 percent annual productivity growth before 1973 but only 1 percent afterward, nobody really knows why Japan surged from defeat to global economic power after World War II, while Britain slid slowly into third-rate status. At any given time there are always policy entrepreneurs willing to claim that they have all the answers, but we'll come to that story in later chapters.
The other mystery is the reason why there is a business cycle ― the irregular rhythm of recessions and recoveries that prevents economic growth from being a smooth trend. It was in challenging the orthodox, Keynesian view of business cycles that conservatives first forced a major rethinking of economics.

What saved the economy, and the New Deal was the enormous public-works project known as World War II, which finally provided a fiscal stimulus adequate to the economy's needs.