Exactly how low can mortgage rates go?  A Record-breaking low, according to Freddie Mac's (FRE) Primary Mortgage Market Survey released Thursday, which showed an eleventh consecutive week of falling rates, where 30-year fixed-rate mortgages averaged an astoundingly low 4.96 percent with an average 0.7 point, down from 5.01 percent last week and 5.69 percent a year ago. “Interest rates for 30-year fixed rate mortgages fell for the 11th straight week to another record low, due in part to the slowing economy and government actions,” said Frank Nothaft, Freddie Mac vice president and chief economist.  “So far, both the U.S. Treasury Department and the Federal Reserve have added over $100 billion in liquidity to the mortgage market since September 2008, which put downward pressure on interest rates for fixed-rate mortgages. " “In December, the unemployment rate rose to 7.2 percent, the highest since January 1993, and the economy lost 2.6 million jobs over 2008, the largest annual drop since 1945.  That brought down yields on Treasury securities and mortgage rates followed,” Nothaft said. One-year Treasury-indexed ARMs fell to 4.89 percent this week from 4.95 percent last week, according to the GSE's weekly survey. Five-year Treasury-indexed ARMs also dropped, averaging 5.25 percent this week compared to last week's 5.49 percent. The 5-year ARM has not been lower since the week ending September 8, 2005, when it averaged 5.24 percent. Despite record-setting lows on most mortgage rates, 15-year fixed-rate mortgages actually rose this week, averaging 4.65 percent with 0.7 point, up slightly from last week's 4.62 percent, Freddie mac said. Bankrate.com's weely mortgage rate survey also found that 15-year fixed-rate mortgages increased. The benchmark on 30-year fixed-rate mortgages, on the other hand, fell 5 basis points to 5.28 percent, matching the survey's record low, according to Bankrate. Nothaft said Thursday the Federal Reserve may add up to an additional $570 billion in liquidity to the mortgage market this year, based on its November 25, 2008 announcement, which would further shore up mortgage lending and keep rates low. Just how low will they go? 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.