Average long-term U.S. mortgage rates rose this week for the sixth straight week, marking new highs not seen in 15 years, before a crash in the housing market triggered the Great Recession.

Mortgage buyer Freddie Mac reported Thursday that the average on the key 30-year rate climbed to 6.70% from 6.29% last week. By contrast, the rate was 3.01% a year ago. The average rate on 15-year, fixed-rate mortgages jumped to 5.96% from 5.44% last week.

Freddie Mac noted that for a typical mortgage amount, a borrower who locked in at the higher end of the range of weekly rates over the past year would pay several hundred dollars more than a borrower who locked in at the lower end of the range.