WASHINGTON (AP) — Average long-term U.S. mortgage rates edged slightly lower this week after rising for three straight weeks.

Mortgage giant Freddie Mac said Thursday the average rate on a 30-year fixed-rate mortgage ticked down to 3.84 percent this week from 3.85 percent a week earlier. The rate on 15-year fixed-rate mortgages slipped to 3.05 percent from 3.07 percent.

Last week both rates reached their highest level since mid-March, rising along with the yield on 10-year Treasury notes — reflecting some signs of improvement in the U.S. economy. The unemployment rate dropped last month to 5.4 percent, the lowest since May 2008.

Still, mortgage rates remain low by historic standards. A year ago, the 30-year rate was 4.14 percent and the 15-year was 3.25 percent.

A separate report out Thursday showed that sales of existing U.S. homes slipped in April due to relatively few listings and rising prices, a trend that could weigh on the recovering housing market. The National Association of Realtors said sales of existing homes fell 3.3 percent last month to a seasonally adjusted annual rate of 5.04 million.

April marked the second straight month of the sales rate topping 5 million homes. Purchases have recovered from a disappointing 2014 because strong job growth and low mortgage rates have generated more would-be buyers. But greater demand in recent months has failed to convince more people to list their properties for sale.

At the same time, builders broke ground on homes in April at the fastest pace in more than seven years. The government reported Tuesday a surprising 20.2 percent jump in residential construction, to a seasonally adjusted annual pace of 1.14 million.

The stepped-up construction reflected a rebound from a dismal winter that shut down construction sites, and it improves the likelihood that the U.S. economy will accelerate after likely shrinking early this year.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country at the beginning of each week. The average doesn’t include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for a 30-year mortgage rose to 0.7 point this week from 0.6 point last week. The fee for a 15-year loan was unchanged at 0.6 percent.

The average rate on five-year adjustable-rate mortgages slipped to 2.88 percent from 2.89 percent; the fee remained at 0.5 point. The rate on one-year ARMs averaged 2.51 percent, up from 2.48 percent last week; the fee was unchanged at 0.4 point.