The Trigger

"While the roots of the crisis were global, it was securitized US subprime mortgages that served as the crisis' immediate trigger. The surge in demand for mortgage-backed securities was heavily driven by Fannie Mae and Freddie Mac, which were pressed by the department of Housing and Urban Development and the Congress to expand affordable housing commitments. The enormity of these purchases was not revealed until Fannie Mae in September 2009 reclassified a large part of its prime mortgages securities portfolio as subprime." -Alan Greenspan