WASHINGTON — Average long-term U.S. mortgage rates fell for the third straight week, with the benchmark 30-year rate again marking its lowest level since May 2013. The average for a 15-year mortgage, a popular choice for people who are refinancing, dipped below 3 percent for the first time since then.

Mortgage company Freddie Mac says the nationwide average for a 30-year mortgage slid to 3.66 percent this week from 3.73 percent last week. The rate for the 15-year loan declined to 2.98 percent from 3.05 percent last week.

The ongoing decline in rates lured a crop of prospective buyers, as applications for mortgages marked their biggest weekly gain last week in over six years. Applications jumped 49.1 percent, the biggest weekly increase since November 2008, according to the Mortgage Bankers Association.