WASHINGTON (AP) — Average long-term U.S. mortgage rates declined this week, approaching their lows for the year.Mortgage company Freddie Mac said Thursday the nationwide average for a 30-year loan slipped to 4.12 percent from 4.14 percent last week. The average for a 15-year mortgage, a popular choice for people who are refinancing, fell to 3.24 percent from 3.27 percent last week.Mortgage rates are below the levels of a year ago. They have fallen in recent weeks after climbing last summer when the Federal Reserve began talking about reducing the monthly bond purchases it was making to keep long-term borrowing rates low.Mortgage rates often follow the yield on the 10-year Treasury note.