Reuters

We have an ER problem.

Too many people use them for routine care, and too many people use them because they're uninsured. Now, these sound like the same problem. Maybe people use emergency rooms for routine care because they don't have insurance. And maybe giving them insurance will let them get cheaper preventative care instead of more expensive ER care. That is, maybe insuring the uninsured will pay for itself!

Well, no.

Five years ago, Oregon did something that was equal parts depressing and scientific genius. It held a Medicaid lottery. See, the state had money to expand its Medicaid system, but not enough to meet all the demand for it. So they had people draw numbers. That's the depressing part. The genius part is there wasn't any difference between the uninsured people who did and didn't win Medicaid coverage. It was just luck—which is another way of saying a randomized controlled trial. That's let researchers test what getting insured does and doesn't do.

It turns out one thing getting insured does is increase ER visits. Indeed, a new paper in Science finds that people who won Oregon's Medicaid lottery went to the ER 40 percent more than people who lost it in the two years after. So much for the idea that being insured will save money by cutting down on trips to the ER.