The federal Government Accountability Office just dropped a bombshell: Increasingly widespread income-driven student loan repayment programs may cost taxpayers far more than the Department of Education predicted. Part of the problem has been major expansion of such programs, and part just bad modeling by the department. It’s all about to become education secretary designee Betsy DeVos’ problem.

According to a new GAO report, the federal government is expected to lose $74 billion on Direct Loans — loans right from the federal Treasury — made between 1995 and 2017 that have been included in income-driven repayment plans. Such plans enable borrowers to pay back their loans based on their income instead of set monthly payments. The goal is to keep repayment affordable, but the plans — there are five right now, as well as several other non-income-driven repayment programs — tend to be rather generous, including forgiveness after 20 or 25 years, and capping payments at 10 to 20 percent of borrowers’ discretionary income.