The present crisis is the bottom of a recurring problem that I call the leverage cycle, in which leverage gradually rises too high then suddenly falls much too low. The government must manage the leverage cycle in normal times by monitoring and regulating leverage to keep it from getting too high. In the crisis stage the government must stem the scary bad news that brought on the crisis, which often will entail coordinated write downs of principal; it must restore sane leverage by going around the banks and lending at lower collateral rates (not lower interest rates), and when necessary it must inject optimistic capital into ﬁrms and markets than cannot be allowed to fail. Economists and the Fed have for too long focused on interest rates and ignored collateral.
Geanakoplos, John, "Solving the Present Crisis and Managing the Leverage Cycle" (2010). Cowles Foundation Discussion Papers. 2079.