Part of this search for yield led to rapid growth in the demand for, and development of, more complex structured financial products, such as collateralized debt obligations (CDOs) backed by asset-backed securities or by other CDOs, and asset-backed commercial paper (ABCP) backed by CDOs, some of which (after 2000) were based on U.S. subprime mortgages.
1 These complex instruments were rated by credit-rating agencies using the same scale that they had used in the past for plain-vanilla corporate debt. Some sellers of these complex financial instruments emphasized that these products were highly rated – many were AAA – but placed little emphasis on their other features.