After sliding downward for 11 straight weeks, mortgage rates rose last week -- and remained virtually unchanged through this week, according to Freddie Mac's (FRE) Primary Mortgage Market Survey released Thursday. 30-year fixed-rate mortgages averaged 5.10 percent with an average 0.7 point this week, dropping just slightly below last week's 5.12 percent average. Last year at this time, the 30-year fixed-rate mortgage average sat higher at 5.68 percent. 15-year fixed-rate mortgages averaged 4.8 percent this week, unchanged from last week's identical posting, but below the year ago reading of 5.17 percent. “Mortgage rates held steady this week,” said Frank Nothaft, Freddie Mac vice president and chief economist.  “The index of leading indicators rose 0.3 percent in December, the first increase in 6 months, fueled by an expansion in the money supply.  However, the Federal Reserve acknowledged in its January 28th policy committee statement that since December the economy has weakened further." “Both the S&P/Case-Shiller 20-city composite index...and the National Association of Realtors data... indicate sharply lower house prices across many U.S. metropolitan areas," Nothaft said. "At the same time, interest rates for 30-year fixed-rate mortgages reached a 50-year low toward the end of December.  These two factors contributed to housing affordability reaching its highest level since 1973...and help to explain the 7.0 percent increase in existing home sales in December.” One-year Treasury-indexed ARMs also moved very little this week, according to Freddie Mac's report, falling from 4.92 last week to 4.9 percent. Five-year Treasury-indexed ARMs climbed -- but just barely -- from 5.24 to 5.27 percent. Bankrate.com's weekly mortgage rate survey found the 30-year fixed rate benchmark as well as the 15-year fixed rate benchmark dropped, but only 11 and 10 basis points, respectively. Regardless of the slight changes this week, mortgage rates still remain at near all-time lows, and combined with falling home prices, houses are more affordable said Bankrate's Holden Lewis. "Well, affordable for people who can make substantial down payments," he said. Write to Kelly Curran at kelly.curran@housingwire.com. Disclosure: The author held no relevant investment positions when this story was published. Indirect holdings may exist via mutual fund investments. HW reporters and writers follow a strict disclosure policy, the first in the mortgage trade.