U.S. homeowners are doing a better job of keeping up with their mortgage payments, aided by an improving housing market and low interest rates that are making it easier  to refinance  BusinessWeek  reported. According to credit reporting agency TransUnion, the percentage of mortgage borrowers at least two months behind on their payments fell in the third quarter to 5.41 percent, the lowest point in more than three years. The rate was down from 5.49 percent in the second quarter and was nearly 8 percent below the 5.88 percent rate in the third quarter last year, the company said.