Much of the justification for an individual health insurance mandate, like that pushed by Massachusetts Governor Mitt Romney and the Heritage Foundation, is that people who lack insurance in the current system still receive medical treatment when needed. The cost of treating these “free riders” is shifted to the insured and the taxpayer. In particular, it is suggested that these uninsured individuals will end up at hospital emergency rooms. Advocates of universal single-payer systems often make similar arguments.

But a new study in Health Affairs shows that that there is no significant difference in emergency room use between insured and uninsured populations. The study concludes that increases in the number of uninsured are not likely to lead to an increase in emergency room visits. However, the study does show that Medicaid beneficiaries use emergency rooms more than either the insured or the uninsured. This may result both from the difficulty that Medicaid patients have in finding primary-care physicians willing to treat them at Medicaid’s low reimbursement rates, and from the fact that emergency room visits are essentially free for the Medicaid patient.

One other finding is worth noting as well. Contrary to public perception, noncitizen immigrants actually use emergency rooms less than citizens. Emergency rooms are not being overrun by illegal immigrants.