40 percent. That’s how much unnecessary emergency room visits increased among a tested population of Oregonians who were given access to Medicaid compared to a population of low-income uninsured citizens. Michael Cannon of the Cato Institute explains it here:
The Oregon Health Insurance Experiment is the gold standard among studies on the effects of health insurance. It followed thousands of Oregon low-income adults who had been randomly assigned to receive either Medicaid or no health insurance coverage, and measured the differences between the two groups. Such random assignment allows researchers to isolate the effects of Medicaid without interference from potentially confounding variables present in other studies.
Writing in Science, the Oregon Health Insurance Experiment researchers found that Medicaid did increase the use of preventive and primary-care services, but emergency-room use rose as well. Over an 18-month period, 100 low-income, uninsured adults in the Portland area would visit the ER about once each, on average. When Medicaid made health care “free” these households, they made an additional 40 visits over that period — a 40-percent increase.