Freddie Mac CEO Donald Layton said that home prices have been reasonably strong over the past five years or so, but a new construction lag is what’s really contributing to the lack of affordable housing.He also said there’s been a noticeably higher rate of home price growth than in average or median family income. Layton said, in the long-term, the U.S. has produced 1.5 million housing units a year, both multifamily and single-family. And with a small population growth adjustment, Layton said it should be about 1.6 million a year now. “I believe it has noticeably declined in the financial crisis and it has never returned to that level again,” he said in a phone interview.