Borrowing costs have trended lower for some U.S. consumers in recent months, especially home buyers. Average interest on a 30-year, fixed mortgage was 4.31 percent on March 14, down 4.62 percent after the Federal Reserve’s most recent rate increase in December, Freddie Mac reports. Market participants say mortgage rates have tracked yields on 10-year U.S. Treasury notes, which dipped to 2.61 percent yesterday. Rates on auto loans also have retreated of late, with the average interest on a five-year new-car loan falling to 4.74 percent in mid-March from 4.96 percent in the wake of the December rate hike, according to Bankrate. Meanwhile, the cost of variable-rate credit card debt increased to 17.84 percent a year as of last week from 17.59 percent in late December.