Earlier this week, the College Board released its data on the rising cost of college. The numbers were striking. In the past year alone, tuition for four-year public universities rose 8.3 percent for in-state students and 5.7 percent for out-of-state students. Some of those hikes are likely due to state budget cutbacks, but the same thing occurred with private colleges — a 4.5 percent tuition increase in the past year.

Those figures are stunning. But what’s especially mind-boggling is this chart from Matthew Philips over at Freakonomics. You’ve all heard about the high-octane rise in health care costs, right? Well, since 1978, college tuition and fees have been getting expensive at a much, much faster rate than even medical care:

So what gives? As far back as 1993, experts were observing that tuition was rising so fast because parents were willing to swallow the cost. More recently, a U.S. News & World Report story from 2009 argued that prices were ballooning at elite universities because they’re all in a bidding war for top faculty and better services for students. That competition for students has also forced schools to hand out bigger and bigger scholarships, raising the sticker price of education. Meanwhile, Ronald Ehrenberg, a labor economist at Cornell, has blamed “the shared system of governance between trustees, administrators, and faculty” at many private universities, which “guarantees that selective private institutions will be slow to react to cost pressures.” Whatever the reason, those tuition trends don’t seem to be slowing anytime soon.