Two months after the beginning of the credit crisis, the monetary policy establishment has reached a consensus on its causes: the complexity of some of the instruments, shortcomings in the mathematical models, weakness in risk management and, of course, the role of the ratings agencies. In other words: someone else.

I concede that each one of these factors contributed to this crisis. But to blame ratings agencies is like blaming shopkeepers for inflation. If you look for an underlying cause of this credit bubble, one of the biggest of all time, then surely you are looking at something bigger than a couple of ratings agencies. I believe that the explosive growth in credit derivatives and collateralised debt obligations between 2004 and 2006 was caused by global monetary policy between 2002 and 2004.