The Fed didn't ramp up its initial asset purchase programme above $1 trillion until March of 2009, at which point the economy had already lost some 6m jobs. Why the delay? One data point worth noting: the monthly core inflation rate was positive throughout 2008 and 2009. NGDP growth, by contrast, was already negative in the third quarter of 2008, and was sharply negative in the fourth quarter of that year, when total spending in the economy shrank at an 8.4% annual pace. A central bank with an explicit NGDP level target would have faced (appropriately) intense pressure to do much more much sooner than one with the Fed's present, vague focus on an inflation target as a means to broader macroeconomic stability.