NEW YORK (CNN/Money) - U.S. mortgage rates dropped as signs of inflation remained dormant in the world's largest economy, which should keep rates affordable for the first half of the year, according to mortgage finance firm Freddie Mac.

The 30-year mortgage fell to 5.64 percent from 5.66 percent last week with 0.6 of a point payable up front. The 30-year averaged 5.91 percent a year earlier. It's the lowest rate for the 30-year since last July 11.

The 15-year mortgage dropped to 4.95 percent, also with 0.6 of a point payable up front. Last week the 15-year averaged 4.97 percent and a year earlier it averaged 5.31 percent. It's the lowest rate for the 15-year since last July 11.

The one-year adjustable rate mortgage (ARM) averaged 3.56 percent, with 0.7 of a point payable up front, down from 3.62 percent. A year earlier. It's the lowest rate for the ARM since July 18; a year earlier, it averaged 3.93 percent.

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"Mortgage rates remain low as the economy picks up steam allowing families a chance to purchase a new home or refinance if they haven't yet," said Frank Nothaft, Freddie Mac's chief economist. "With low prospects of inflation increasing anytime soon, mortgage rates should remain affordable over the first half of this year."

Freddie Mac's average mortgage rates are based on a survey of 125 lenders nationwide. The rates include those on mortgages accepted by borrowers with good credit ratings who place a 20 percent down payment on their homes, according to Freddie Mac.

Freddie Mac (FRE: up $1.69 to $64.90, Research, Estimates), or Federal Home Loan Mortgage Corp., is a publicly traded company the government established in 1970 to provide a flow of funds to mortgage lenders. It buys mortgages from banks, bundles them and then resells them as mortgage-backed securities.

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