CHICAGO (MarketWatch) -- Mortgage rates rose this week, following bond yields as signs of an improving economy emerge, Freddie Mac's chief economist said on Thursday.

The 30-year fixed-rate mortgage averaged 4.94% for the week ending Dec. 17, up from last week's 4.81% average; the mortgage averaged 5.19% a year ago, according to Freddie Mac's weekly survey of conforming mortgage rates. And 15-year fixed-rate mortgages averaged 4.38%, up from 4.32% last week; they averaged 4.92% a year ago.

Five-year Treasury-indexed hybrid adjustable-rate mortgages averaged 4.37% this week, up from 4.26% last week; they averaged 5.60% a year ago. One-year Treasury-indexed ARMs averaged 4.34%, up from 4.24% last week; the ARMs averaged 4.94% a year ago.

To obtain the rates, the 30-year fixed-rate mortgage required payment of an average 0.7 point, the 15-year fixed-rate mortgage and the 5-year ARM required an average 0.6 point and the 1-year ARM required an average 0.5 point. A point is 1% of the mortgage amount, charged as prepaid interest.

"Mortgage rates followed bond yields higher once again this week amid signs of an improving economy," said Frank Nothaft, Freddie Mac chief economist, in a news release. "On the consumer side, retail sales jumped 1.3% in November and consumer sentiment, as measured by the University of Michigan, rose above the market consensus forecast to the highest reading since September. Industrial production also showed large gains in November."

Nothaft said that average rates on 30-year fixed-rate mortgages have been below 5% over the past seven weeks, contributing to a boost in refinance activity.

"Roughly three out of four mortgage applications were for refinancing during the first two weeks of December, according the Mortgage Bankers Association," he said. Read the latest mortgage data from the MBA.