Students who haven’t graduated are more than four times as likely to default on their student loans as those who have, according to a study by the think tank Education Sector.

Recent research from the economist Beth Akers shows that borrowers with less than $5,000 in student debt are the most likely to be late on payments. In fact, the more college debt a student incurs, the less likely he or she is to default. This may seem counterintuitive, but it’s not—a low loan balance is indicative of a borrower who didn’t complete school, and is therefore less likely to repay. According to Department of Education statistics, defaulters also tend to be older (the median age is thirty-eight), from low-income backgrounds, with poor financial literacy, and with no degree to show for their efforts. A disproportionate number of them attended for-profit colleges.

This is all evidence of a large crisis in American higher education: we have a big college completion problem. More than thirty-one million adults have earned college credit within the last twenty years but left without any post-secondary credential. By 2012, only 59 percent of students seeking a bachelor’s degree graduated within six years. For students seeking a certificate or degree at a two-year institution, the completion rate was 31 percent.