The average long-term U.S. mortgage rate fell again this week, but remains near the 22-year high it hit three weeks ago, little relief for house hunters facing a market held back by persistently high prices and a near-historic low number of homes for sale. Mortgage buyer Freddie Mac said Thursday that the average rate on the benchmark 30-year home loan fell to 7.12% from 7.18% last week. A year ago, the rate averaged 5.89%. High rates can add hundreds of dollars a month in costs for borrowers, limiting how much they can afford in a market already unaffordable to many Americans.