Credit rating agencies (CRAs) — firms which rate debt instruments/securities according to the debtor’s ability to pay lenders back — played a significant role at various stages in the American subprime mortgage crisis of 2007-2008 that led to the Great Recession of 2008-2009. The new, complex securities of “structured finance” used to finance subprime mortgages could not have been sold without ratings by the “Big Three” rating agencies — Moody’s Investors Service, Standard & Poor’s, and Fitch Ratings. A large section of the debt securities market — many money markets and pension funds — were restricted in their bylaws to holding only the safest securities — i.e securities the rating agencies designated “triple-A”. The pools of debt the agencies gave their highest ratings to included over three trillion dollars of loans to homebuyers with bad credit and undocumented incomes through 2007. Hundreds of billions of dollars’ worth of these triple-A securities were downgraded to “junk” status by 2010, and the writedowns and losses came to over half a trillion dollars. This led “to the collapse or disappearance” in 2008-9 of three major investment banks (Bear Stearns, Lehman Brothers, and Merrill Lynch), and the federal governments buying of $700 billion of bad debt from distressed financial institutions.