Bernanke, Ben

The immediate trigger of the crisis, as you know, was a sharp decline in house prices, which reversed a previous run-up that had been fueled by irresponsible mortgage lending and securitization practices. Policymakers at the time, including myself, certainly appreciated that house prices might decline, although we disagreed about how much decline was likely; indeed, prices were already moving down when I took office in 2006. However, to a significant extent, our expectations about the possible macroeconomic effects of house price declines were shaped by the apparent analogy to the bursting of the dot-com bubble a few years earlier. That earlier bust also involved a large reduction in paper wealth but was followed by only a mild recession. In the event, of course, the bursting of the housing bubble helped trigger the most severe financial crisis since the Great Depression. It did so because, unlike the earlier decline in equity prices, it interacted with critical vulnerabilities in the financial system and in government regulation that allowed what were initially moderate aggregate losses to subprime mortgage holders to cascade through the financial system. In the private sector, key vulnerabilities included high levels of leverage, excessive dependence on unstable short-term funding, deficiencies in risk measurement and management, and the use of exotic financial instruments that redistributed risk in nontransparent ways. In the public sector, vulnerabilities included gaps in the regulatory structure that allowed some systemically important firms and markets to escape comprehensive supervision, failures of supervisors to effectively use their existing powers, and insufficient attention to threats to the stability of the system as a whole.