Social Explorer; Federal Housing Finance Agency House Price Index (HPI).
House Price Index Technical Documentation
15. Why is the FHFA HPI based on Fannie Mae or Freddie Mac mortgages?
FHFA has access to this information by virtue of its role as the federal regulator responsible for these government-sponsored enterprises. Chartered by Congress for the purpose of creating a reliable supply of mortgage funds for homebuyers, Fannie Mae and Freddie Mac are the largest mortgage finance institutions in the U.S. representing a significant share of total outstanding mortgages.