Politicians who complain about college costs frequently cite two numbers: one trillion and seven million. Student borrowers owe more than $1 trillion, and seven million borrowers are in default, according to the latest Department of Education data.

It’s natural for people listening to the politicians to connect the two facts with a causal arrow: More debt leads to more default. But the reality is surprising: Borrowers who owe the most are least likely to default.

The reason for this strange pattern? The biggest borrowers tend to become the highest earners.

In particular, borrowing is highest for those who go to graduate school. Forty percent of new loans go to graduate students. Among those earning law and medical degrees in 2012, median debt (undergraduate and graduate school) is $141,000 for lawyers and $162,000 for doctors.