Asset-backed securities (ABS) finance pools of familiar asset types, such as auto loans, aircraft leases, credit card receivables, mortgages, and business loans. In one way or another, these asset types represent contractual obligations to pay.

The Federal Reserve is the single largest agency MBS investor through its large-scale asset purchase program, with total holdings of $2.5 trillion as of October 2021. Research has found that Fed MBS purchases reduce MBS yields and have a range of other effects on financial markets and the macroeconomy (see section 4).

Ginnie Mae, backed by the full faith and credit of the U.S. government, guarantees that investors receive timely payments. Fannie Mae and Freddie Mac also provide certain guarantees and, while not backed by the full faith and credit of the U.S. government, have special authority to borrow from the U.S. Treasury.