WASHINGTON (AP) — More Americans are falling behind on student loans, threatening their ability to obtain mortgages and other credit in the future.

The Federal Reserve Bank of New York says more than 31 percent of people with student loans at the end of last year were 90 or more days delinquent. That compares with less than 25 percent at the end of 2008.

Student loans were the only type of credit to increase through the Great Recession and afterward. Student debt amounted to $966 billion at the end of last year, up 34 percent from four years earlier.

Meanwhile, delinquency rates for other categories of loans are improving. The percentage of borrowers behind on mortgages, home equity and auto loans fell from the July-September quarter of last year to the October-December quarter.