Interest rates on long-term U.S. mortgage loans fell to their lowest level in three months last week, according to data from Freddie Mac. During the week ended December 13, the average rate on a 30-year fixed-rate mortgage dropped to 4.63% with an average 0.5 point, down from 4.75% the previous week. One year ago, it was lower still at 3.93%. Rates have fallen for the past month as investors, nervous about foreign economies, have turned to the safety of bonds.