The Federal Home Loan Bank Board collected average mortgage rate data from financial institutions around the country until 1989. The National Average Contract Mortgage Rate data is now collected by the Federal Housing Finance Agency, and a chart of monthly average mortgage rates for single-family resale homes through 2012 is available on the agency's website at FHFA.gov.
Every month, the FHFA collects data from savings associations, mortgage companies, commercial banks, and savings banks about the interest rates, loan terms and house prices of loans that were closed in the preceding month. It also collects quarterly mortgage data about conventional loans for each Federal Home Loan Bank district and for many metropolitan areas, according to FHFA.gov. Adjustable rate mortgages are most commonly based on the National Average Contract Mortgage Rate by many lenders. Originally, it was the only index that federally chartered savings and loan associations were allowed to use for adjustable rate mortgages.
Other organizations, such as Freddie Mac and the Mortgage Banker's association, also compile historical average mortgage data from their participating institutions, and an example of these charts side-by-side is available at MortgageNewsDaily.com. The charts are interactive and allow site visitors to compare the indexes to one another.