I think that Arnold Kling here describes the major problem with most schools of macroeconomic thought:
DeLong is of course living in the macroeconomic world where we do not worry about Recalculation. Instead, we all work in one giant GDP industry, and for some mysterious reason many of our GDP factories have shut down, so that government must build and operate some GDP factories to keep us all employed.
Thanx and a tip o' the hat to Steve Sailer.
That is all.