"Monetary excesses were the main cause of the boom. The Fed held its target interest rate, especially in 2003-2005, well below known monetary guidelines that say what good policy should be based on historical experience. Keeping interest rates on the track that worked well in the past two decades, rather than keeping rates so low, would have prevented the boom and the bust."
You can see the full article at the Wall Street Journal (Feb 9, 2009).
Alan Greenspan, as you would expect, disagrees with John Taylor and claims that the central bank was doing the right thing but the problem was the disconnect between short-term interest rates and mortgage rates (which were being kept too low partly because of the increase in saving rates coming from Asia).
"Given the decoupling of monetary policy from long-term mortgage rates, accelerating the path of monetary tightening that the Fed pursued in 2004-2005 could not have "prevented" the housing bubble. All things considered, I personally prefer Milton Friedman's performance appraisal of the Federal Reserve. In evaluating the period of 1987 to 2005, he wrote on this page in early 2006: "There is no other period of comparable length in which the Federal Reserve System has performed so well. It is more than a difference of degree; it approaches a difference of kind.""
You can see the full article at the Wall Street Journal (March 11, 2009).
Lucas Papademus, Vice President of the ECB looks forward in a recent speech (May 15, 2009) and asks what monetary policy should do in a similar future situation. He advocates for a symmetric reaction of monetary policy: not only it makes sense to lower rates when the crisis starts but central banks should also act when financial imbalances are accumulating.
"In order to reduce such potentially dangerous side-effects of non-standard measures of liquidity provision and of the very low policy rates during a crisis, monetary policy would have to be sufficiently tightened during the financial boom phase. Such a policy would dampen financial market excesses through two channels. It would tend to reduce asset prices by increasing the rate at which an asset’s future income stream is discounted. Most importantly, the anticipation of such a policy response would reduce the likelihood of a speculative bubble emerging in the first place, by affecting investment behaviour and reducing the level of risk incurred by financial intermediaries in their lending."
Papademus falls short of making a statement on whether interest rates were too low during the years that preceded the crisis (as Taylor argues). But his argument supports the view that standard monetary policy (i.e. via interest rates) also has a role to play in dealing with speculative bubbles in financial markets, it is not just a matter of proper regulation and supervision.