WASHINGTON (AP) — U.S. mortgage rates crept slightly higher this week but remain at low levels that could encourage more home-buying.

Mortgage buyer Freddie Mac said Wednesday that the average rate on a fixed 30-year mortgage ticked up to 3.68% from 3.66% the previous week. The average 15-year mortgage was unchanged at 3.15%.

Borrowing costs have fallen sharply in the past year, helping lift home sales and construction. The 30-year rate was 4.8% at the same time last year, while the 15-year rate was 4.25%. Sales of existing homes increased 4.6% in October compared with a year ago, while new home sales have soared by more than 30%.

Freddie Mac surveys lenders across the country between Monday and Wednesday each week to compile its mortgage rate figures.