U.S. mortgage rates jumped this week to the highest level in seven years, a trend that is pulling down home sales and slowing home price growth. Mortgage buyer Freddie Mac said Thursday that the average rate on a 30-year, fixed rate mortgage rose to 4.94 percent, from 4.83 percent last week. A year ago the rate was 3.9 percent. The average rate on a 15-year, fixed rate loan increased to 4.33 percent, from 4.23 percent last week. Higher rates have kept many would-be purchasers on the sidelines. Sales of existing homes have fallen for six straight months, and sales of newly-built homes have declined for four months. Freddie Mac says home price increases are slowing as a result, particularly in higher-priced coastal cities.