Both Alan Greenspan and Ben Bernanke have claimed that monetary policy was not responsible for the housing bubble. Instead, they blame a change in the relationship between short-term interest rates and long-term mortgage rates. An article in the Economist that summarizes their positions states part of the Greenspan explanation as follows: “The rise in desired global saving relative to desired investment caused a global decline in long-term rates, which became delinked from the short-term rates that central bankers control.” How would the decoupling of short- and long-term rates create a problem for monetary policy and policy rules?