The Federal Housing Finance Agency has data on current and historical average mortgage rates.
Mortgage Market Statistical Annual: contains data on mortgage rates, origination activity, servicers, sub-prime originations, and Fannie Mae and Freddie Mac activity. There are print copies of this title in the Stamps Reading Room at the Baker Business Library: call #Ref. HG4655 .M67. However, the Table of Contents is available online from the Inside Mortgage Finance website, and can aid in requesting a scan of relevant pages through the Scan & Deliver link in the HOLLIS record for this title.
