The financial tsunami of 2007 and 2008 left a trail of economic wreckage in its wake with which the US and Europe will be reckoning for years. Cleaning up this wreckage has been the subject of the most consequential debate among economists we’ve seen in decades.

For the Keynesian hardcore of macroeconomists, the problem we face is simple. The US and other developed economies currently face a shortage of "aggregate demand". We are therefore producing much less, in aggregate, than our capacity to produce, in aggregate. The composition of the aggregate doesn't matter. The economy is essentially one giant factory producing GDP widgets.