Forget classes and books, simply existing in college has gotten way more expensive.

The price of room and board, which typically covers housing on-campus and food, roughly doubled (in inflation-adjusted dollars) between 1980 and 2014 at public and private four-year colleges, according to an analysis by the Urban Institute released Tuesday. The rapid rise in the cost of room and board is a relatively new phenomenon; between 1964 and 1980, the price was relatively flat in inflation-adjusted dollars.

“Americans are concerned about college affordability, but public discussions focus on tuition and fees,” said Matthew Chingos, a senior fellow at the Urban Institute and one of the authors of the report. “It turns out that room and board charges have increased a lot.”

Often highly-touted affordability initiatives do little to combat the rising cost of living at college. Tuition freezes, government free college programs and many scholarships and grants often don’t cover basic necessities like housing and food. So the rising costs of room and board can have major implications for the way families pay for college. When students can’t cover living costs they may take on more debt or work several jobs to get through school.

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Chingos’s data, which doesn’t cover the cost of housing and food where most students live -- off-campus -- provides little explanation for why colleges have raised the price of room and board so quickly. But he has some theories. The cost may be going up because colleges reduced the amount they’re subsidizing the cost of living for students, or officials may believe it’s easier to hide price increases in room and board prices than in the cost of tuition and fees. If you’re willing to give colleges the benefit of the doubt, it’s possible that the costs are going up because it truly costs more than in the past to run a dorm and dining hall, he said. Or perhaps the students themselves are partially to blame by demanding amenities and dining options that necessarily cost more.

There are signs that colleges are increasingly turning to these campus amenities to bring in revenue. Media reports over the past few years have highlighted the ways in which colleges use campus dining contracts as leverage to get companies to pay for capital improvements. Critics say the cost of the contracts then gets passed on to students.