About four million people have been added to Medicaid, the government-run single-payer health plan for the poor, since Obamacare rolled out in October. Putting people on Medicaid was a big part of how the Affordable Care Act was supposed to extend affordable health coverage. Extending coverage, in turn, was supposed to save money by cutting down on how often uninsured people went to expensive hospital emergency rooms for care instead of going to a doctor.

But new findings from a top-notch study in Oregon finds that putting people on Medicaid doesn’t cut down on how often they use costly emergency rooms. It increases it, by about 40 percent.

“When you make ER care free to people, they consume more of it. They consume 40 percent more of it," Michael Cannon of the Cato Institute told National Public Radio. “Even as they're consuming more preventive care. And so one of the main arguments for how Obamacare was going to reduce health care costs is just flat out false.”

Avik Roy, in Forbes, points out that this isn’t an accident. This is how Medicaid is supposed to work:

“The authors of the 1965 Medicaid legislation believed that it was morally wrong to expect poor people to pay even modest sums for their own health care. . . . Because Medicaid was nearly free to the program’s enrollees, those enrollees ended up seeking—and receiving—lots of inappropriate care. That led to massive cost overruns that, even today, are bankrupting state governments. But states have had little flexibility to reform Medicaid’s cost-sharing features. The one thing they have been able to do is pay doctors and hospitals less and less to provide the same care.

“That trend, in turn, has led many doctors to stop accepting new Medicaid patients. So it’s extremely difficult for Medicaid enrollees to get appointments with primary care physicians. They have to spend weeks on the phone to find someone who will treat them.

“Put yourself in the shoes of that Medicaid enrollee. Why would you bother calling primary care docs all day and all week, if you can go to the emergency room and get the same care for the same price? So that’s what Medicaid patients do.”

This costs taxpayers, big time, even as millions are facing higher premiums after they’re dumped on to the Obamacare exchanges. So much for “affordable” care.