WASHINGTON — U.S. long-term mortgage rates dipped this week to the lowest average in more than a year, providing a possible boost to the start of the Spring homebuying season in March.

Mortgage buyer Freddie Mac says the average rate on the benchmark 30-year, fixed-rate mortgage declined to 4.35 percent from 4.37 percent last week. The key 30-year home borrowing rate averaged 4.40 percent a year ago. This week was the lowest average since the week of February 8, 2018.

The average rate this week for 15-year, fixed-rate loans declined to 3.78 percent from 3.81 percent.

Mortgage rates hew closely to changes in the interest charged on 10-year U.S. Treasury notes. Lower borrowing costs should help boost home sales, as rising mortgage rates in 2018 caused homebuying to tumble last year.