 This information is obtained by reviewing repeat mortgage transactions on single-family properties whose mortgages have been purchased or securitized by Fannie Mae or Freddie Mac since January 1975.Since the HPI index only includes houses with mortgages within the conforming amount limits, the index has a natural cap and does not account for jumbo mortgages.The HPI was developed in conjunction with OFHEO's (now FHFA) responsibilities as a regulator of Fannie Mae and Freddie Mac.