Average mortgage interest rates for 30-year, fixed-rate loans declined in the week ending Thursday, the Federal Home Loan Mortgage Corp. said. Average rates for 30-year contracts dropped from 3.71 percent to 3.66 percent with 0.7 points. Thirty-year mortgage rates averaged 4.5 percent the same week of 2011. Average rates on 15-year contracts also fell, dropping from 2.98 percent to 2.95 percent with 0.6 points. A year earlier, rates on 15-year contracts stood at 3.69 percent. Five-year adjustable rate mortgages averaged 2.77 percent in the week with an average 0.6 points, down from an average of 2.8 percent in the previous week. Five-year adjustable rate loans averaged 3.25 percent a year earlier. Average rates on one-year treasury-indexed adjustable mortgages also fell during the week. Interest rates dropped from 2.78 percent to 2.74 percent with an average 0.5 points. A year ago, rates for these loans averaged 2.99 percent.