The current edition of Science contains a study that should terrify all of us who want to see universal access to health services. The rigorous randomised study showed, as the New York Times put it, that “newly insured people actually went to the emergency room a good deal more often” than those without insurance.

As the Times goes on to explain, “the study … compared thousands of low-income people in the Portland area who were randomly selected in a 2008 lottery to get Medicaid coverage with people who entered the lottery but remained uninsured. Those who gained coverage made 40 percent more visits to the emergency room than their uninsured counterparts during their first 18 months with insurance. The pattern was so strong that it held true across most demographic groups, times of day and types of visits, including those for conditions that were treatable in primary care settings.”

This is a shock to many supporters of Obamacare who have claimed that better access to primary care would reduce the demand for expensive hospital care in emergency rooms. Maybe it shouldn’t surprise them. The claim that prevention saves money is old. Aneurin Bevan, the founder of the British National Health Service wrote in 1952, “much sickness and often permanent disability arise from failure to take early action, and this in its turn is due to high costs and the fear of the effects of heavy bills on the family.” But the NHS in 2014 is undergoing yet another crisis in overuse of emergency rooms. A third of British GPs now think that patients should be charged ¬£10 to discourage unnecessary use of casualty departments.

Back when I was studying political science in the late 1970s, we read the late Professor Aaron Wildavsky’s classic textbook, Speaking Truth to Power. In his telling of the evolution of US Medicare in the 1960s, he recalled that the original objective was to improve health but that it soon morphed into assuring better access to health services. Organisations, he thought, always measured what they could actually deliver rather than what they had originally promised to do. “Governments can help equalize the number of times each person … visits the doctor each year. In this way, equality of access to medicine has come to replace improvement in health as the operational objective of government medical programs,” he wrote. This shift meant “that at long last progress can be reported.”

As both the US and middle income countries push for universal access to care, they should not accept comfortable delusions.

Here an illustration from The Guardian of Aneurin Bevan launching the NHS in 1948