Average US rate on 30-year mortgage slides to 3.97 percent; 15-year loan at 3.18 percent

Average U.S. mortgage rates tumbled this week, with the 30-year loan hitting its lowest level since June 2013 as Treasury bond yields marked new lows.

It was the fourth straight week of declines for mortgage rates, making it more affordable to borrow to buy a home.

Mortgage company Freddie Mac says the nationwide average for a 30-year loan dipped to 3.97 percent from 4.12 percent last week. The average for a 15-year mortgage, a popular choice for people who are refinancing, fell to 3.18 percent from 3.30 percent.

The 10-year Treasury noted traded at 2.13 percent Wednesday, down from 2.34 percent a week earlier. Mortgage rates often follow the yield on the 10-year note.