Liberal underwriting was not limited to subprime loans. Alternative-A, or Alt A, mortgages are granted to borrowers with good credit scores who want more flexibility than traditional mortgages offer for the overall level of risk they pose. Prime jumbo loans are larger than government-chartered Fannie Mae or Freddie Mac can buy, or usually $417,000 for single family homes.

Non-agency bonds backed by first mortgages in the Alt-A category total more than $700 billion, trailing the more than $800 billion in subprime debt, according to a March report from analysts at Credit Suisse Group. About $500 billion in jumbo-loan bonds are outstanding, Credit Suisse said.