U.S. mortgage activity rose last week, as long-term interest rates dropped, the Mortgage Bankers Association said Wednesday. The association said mortgage activity rose 4.8 percent in the week, while refinancing activity rose 5 percent. Interest rates for 30-year, fixed-rate conforming mortgages decreased from 3.68 percent to 3.67 percent during the week. Points for 30-year conforming loans rose from 0.43 to 0.5. The average interest rate for 30-year contracts on jumbo loans -- larger than $417,500 -- fell from 3.79 percent to 3.77 percent. Points for 30-year jumbo loans fell from 0.36 to 0.27. Interest rates for 15-year, fixed-rate mortgages fell from 2.92 percent to 2.91 percent, with points holding steady at 0.34. The average rate for 30-year loans backed by the Federal Housing Administration fell from 3.43 percent to 3.37 percent with points rising from 0.52 to 0.55. The average rate for short-term, adjustable-rate mortgages decreased in the week from 2.58 percent to 2.57 percent in the week, with points falling from 0.37 to 0.29, the MBA said.