Legal Dictionary

A measurement used by lenders to determine changes to the Interest rate charged on an adjustable rate mortgage.

Source: U.S. Department of Housing and Urban Development

The index is the measure of interest rate changes that the lender uses to decide how much the interest rate on an ARM will change over time. No one can be sure when an index rate will go up or down. To help you get an idea of how to compare different indexes, the following chart shows a few common indexes over a ten-year period (1977-87). As you can see, some index rates tend to be higher than others, and some more volatile. (But if a lender bases interest rate adjustments on the average value of an index over time, your interest rate would not be as volatile.) You should ask your lender how the index for any ARM you are considering has changed in recent years, and where it is reported.

Source: U.S. Department of Housing and Urban Development

A published interest rate compiled from other indicators such as U.S. Treasury bills or the monthly average interest rate on loans closed by savings and loan organizations. Mortgage lenders use the index figure to establish rates on adjustable rate mortgages (ARMs).

Source: Ginnie Mae