Abstract

ABSTRACT Why did the popping of the housing bubble bring the financial system—rather than just the housing sector of the economy—to its knees? The answer lies in two methods by which banks had evaded regulatory capital requirements. First, they had temporarily placed assets—such as securitized mortgages—in off‐balance‐sheet entities, so that they did not have to hold significant capital buffers against them. Second, the capital regulations also allowed banks to reduce the amount of capital they held against assets that remained on their balance sheets—if those assets took the form of AAA‐rated tranches of securitized mortgages. Thus, by repackaging mortgages into mortgage‐backed securities, whether held on or off their balance sheets, banks reduced the amount of capital required against their loans, increasing their ability to make loans many‐fold. The principal effect of this regulatory arbitrage, however, was to concentrate the risk of mortgage defaults in the banks and render them insolvent when the housing bubble popped.