WASHINGTON (AP) — Mortgage rates slipped this week from the highest level since July and remain at historically low levels that are helping would-be purchasers to buy homes.

Mortgage giant Freddie Mac said Thursday that the average rate for a 30-year fixed-rate mortgage declined to 3.69% from 3.78% last week. That's also down more than a full percentage point from a year ago when it was 4.94%.

Lower rates are helping support the housing market. Sales of existing homes rose nearly 4% in September from a year ago, while new home sales have soared 16% during that time. Yet potential homebuyers still face a shortage of available homes, which is pushing prices higher.

The average rate on a 15-year mortgage fell to 3.13% this week from 3.19% a week ago.