Residential mortgage backed security issuance in the U.S. 2003-2023

The year 2021 saw the peak in issuance of residential mortgage backed securities (MBS), at 3.7 trillion U.S. dollars. Since then, MBS issuance has slowed, reaching 1.1 trillion U.S. dollars in 2023. 

What are mortgage backed securities?

A mortgage backed security is a financial instrument in which a group of mortgages are bundled together and sold to the investors. The idea is that the risk of these individual mortgages is pooled when they are packaged together. This is a sound investment policy, unless the foreclosure rate increases significantly in a short amount of time.

Mortgage risk

Since mortgages are loans backed by an asset, the house, the risk is often considered relatively low. However, the loan maturities are very long, sometimes decades, meaning lenders must factor in the risk of a shift in the economic climate. As such, interest rates on longer mortgages tend to be higher than on shorter loans. The ten-year treasury yield influences these rates, since it is a long-term rate that most investors accept as risk-free. Additionally, a drop in the value of homeowner equity could lead to a situation where the debtor is “underwater” and owes more than the home is worth.