Most economists accept that developed economies have been operating considerably below potential GDP since 2008, but there is much less agreement about the size of the output gap, and what should be done about it. This is obviously crucial. The larger the output gap, the greater the waste of resources (and, from an investor’s point of view, the greater the scope for future growth). Furthermore, the larger the gap, the smaller the budget deficit when economies return to potential, so the greater the scope for fiscal expansion today.
Keynesians have been focused on these issues for a while, and have generally had the better of the argument in the current recession. Recently, their thinking has been developing in some important respects. An example is Paul Krugman’s contribution to a panel discussion on the macroeconomics of recessions at the annual meeting of the American Economic Association in San Diego last week. (Brad DeLong, the panel chairman, has posted a transcript).