The people of the United States carry a whopping $1.2 trillion in college loan debt, and 17% of those debtors are behind on their payments or in default. Despite what you might expect, though, the majority of this financial burden doesn’t fall on your average undergrad. A recent study from the Urban Institute points out that smaller groups of specific students carry a higher amount of debt.

Graduate students

The “average” student loan debt is upwards of $22,000, but that’s due in part to the fact that graduate student debt is included in the calculation. Far more than half of grads who borrow more than $50,000 are graduate students. Doctors and lawyers make up a combined 13% of those carrying high debts.

For-profit school grads

Graduates from for-profit colleges made up only 9% of the graduating collegiate class of 2012, but they made up 25% of the same population carrying $50,000 or more in debt—a disproportionate amount. Graduates from public universities and private nonprofit colleges had lower amounts of debt, proportionally speaking.

Students who don’t graduate

Of the students carrying under $10,000 in debt, nearly 60% of them are those who dropped out of school before finishing. These borrowers are more likely to struggle with payments because they can’t secure high-paying jobs, or default altogether because they feel they shouldn’t have to pay the money back.

It shouldn’t surprise us that people who don’t graduate carry a large proportion of debt, because dropping out isn’t uncommon; 40% of people who start college never complete their four-year degree, even after six years in school.

So how do we respond to these unique populations struggling with student loan debt? The federal government has laid out plans to help people lower their monthly payments based on income. If you make a salary less than 150% of the poverty line, your payment is $0. After that, you pay no more than 20% of your annual income. If you become a public servant, your debt can be completely forgiven after ten years. All of these scenarios, of course, apply to federal loans, not loans obtained through private banks.