Whether a mortgage-backed security (MBS) is backed by a
guarantee depends on who issues the security. An MBS is a security
created through securitization. Through securitization, underlying
assets are loans made to individuals and companies who use the
funds to purchase buildings and homes.
If a large number of mortgagors begin to default on their
mortgages, the lender will have a difficult time passing through
mortgage payments to MBS owners. Depending on how diversified the
underlying pool of mortgages is across demographic and geographic
regions, the risk of a mortgagor defaulting may be mitigated.
However, if a significant number of mortgagors begin to default
on their loans, the mortgagee may default on their MBS. This level
of default will cause investors to suffer, demonstrating the need
for some form of insurance or a guarantee.
Depending on the issuer, an MBS may or may not be guaranteed.
There are four main MBS issuers:
- Fannie Mae (the Federal National Mortgage Association) is
sponsored by the U.S. government and can issue and guarantee MBS
issues. It is a publicly traded company and was established to
maintain capital liquidity and to ensure that low- to middle-income
individuals can purchase homes. Note that Fannie Mae's guarantee is
based on its own corporate health and is not backed by the
government.
- Freddie Mac (the Federal Home Loan Mortgage Corporation) is
similar to Fannie Mae in that it is also sponsored by the U.S.
government and is owned by stockholders. It was created to provide
competition in the secondary mortgage market, which Fannie Mae
originally monopolized. Like Fannie Mae, Freddie Mac can issue and
guarantee MBSs, but its guarantee is not backed by the
government.
- Ginnie Mae (the Government National Mortgage Association)
differs from Fannie Mae and Freddie Mac in that it operates as a
government agency. It does not issue MBSs, and its guarantees are
backed by the full faith and credit of the U.S. government.
Furthermore, Ginnie Mae guarantees MBS issues from qualified
private institutions. Ginnie Mae also has a more stringent
guarantee policy in that it mainly guarantees loans that are
insured by the Federal Housing Administration (FHA) or other
qualified insurers.
- Private issuers also issue MBSs. If a private issuer is
qualified by Ginnie Mae, its issue is guaranteed by that government
agency. If, on the other hand, it is not qualified by Ginnie Mae,
then the MBS issue is not guaranteed.