Mortgage rates continued their decline this week, with the popular 30-year fixed-rate mortgage reaching an average contract interest rate of 4.84 percent — its lowest level of the year so far, according to the latest data from Freddie Mac. Last week, the 30-year FRM came in at 4.93 percent. Meanwhile, its 15-year counterpart averaged 4.24 percent, down from 4.3 percent last year. and the 1-year Treasury-indexed adjustable-rate mortgage averaged 4 percent, down from 4.02 percent last week. This was the lowest interest rate for the 15-year FRM since August 1991 and the lowest for the 1-year ARM since October 2004. Record-low mortgage rates, combined with the homebuyer tax credit, have helped stabilize the housing market, said Frank Nothaft, vice president and chief economist of Freddie Mac. TRD