According to a survey by Freddie Mac, interest rates on U.S. 30-year fixed-rate mortgages, the most widely used loan, averaged 5.14 percent for the week ended Dec. 31, the highest since the week ending Aug. 27 and up from the previous week's 5.05 percent. The 15-year FRM averaged 4.54% with a 0.7 point, up from 4.45% last week and down from 4.83% a year ago. The 5-year Treasury-indexed hybrid adjustable-rate mortgage (ARM) averaged 4.44% with an average 0.6 point, a slight increase from 4.4% last week. The 1-year Treasury-indexed ARM averaged 4.33% this week with a 0.6 point, down from 4.38% last week, according to the survey."Although long-term mortgage rates rose for the fourth week in a row, they still remain affordable by historical standards," Frank Nothaft, Freddie Mac vice president and chief economist, said in a statement. Based on today's median loan amount of $138,000, monthly principal and interest payments for a 30-year fixed-rate mortgage are close to one-third less than a decade ago when rates peaked at 8.6 percent in May 2000, Nothaft said. "This translates into almost 50% less in interest payments over the full 30-year term," he said.