Let me mention one other real-world complication that has made it difficult for the Fed to achieve a faster growth of nominal GDP. Macroeconomists often like to think of inflation in terms of an aggregate price index, the variable P in the equation of exchange. But, particularly in the current environment, aggressive stimulus by the Fed is unlikely to show up as higher wages or the prices of most services, but instead would raise relative commodity prices and could in a worst case scenario precipitate a currency crisis, both of which would be highly destabilizing in their own right. I agree with Sumner that the Fed could and should have done more, but would caution that it is also possible for the Fed to try to do too much. I come back to the perspective with which I opened – given the earlier regulatory lapses, significant economic losses could not have been prevented by any monetary policy that could have been implemented in the fall of 2008.
There are many more points of interest in this dialogue and further comments to come.