The Affordable Care Act gave health insurance to millions of Americans, but studies suggest it did not put a dent in the number of people attending emergency rooms.

On average, emergency departments were responsible for 10% of the medical acute care Americans received between 1996 and 2010, according to a new study in the International Journal of Health Services, and additional data by the National Ambulatory Medical Care Survey. And almost half of care delivered by hospitals and their associated practices is delivered in emergency rooms, the latest study added. The researchers based their findings on data collected by the Centers for Disease Control and Prevention’s National Center for Health Statistics.

One-in-five Americans visit the ER at least once per year, according to the Centers for Disease Control and Prevention and American College of Emergency Physicians, a figure that has remained persistently unchanged. States that chose to expand Medicaid witnessed more ER visits, but fewer visits from people without insurance, another study released in June 2017 in the Annals of Emergency Medicine found. Coverage doesn’t equal access,” said David Marcozzi, a professor at the University of Maryland School of Medicine and co-author of the latest report.

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So why are people still going to emergency rooms instead of seeing a doctor? While nearly 20 million more people gained health insurance as a result of Obamacare, these consumers are not guaranteed to find a nearby doctor who takes their insurance. In particular, many doctors don’t take Medicaid. “Emergency departments are filling the gap,” Marcozzi said, because they are required by law to take any patient regardless of what insurance they have.

Another theory for the persistent visits to emergency rooms: Other studies have shown that having health insurance makes a consumer more likely to see a doctor. “Some people might go into an emergency department not because of a lack of options, but maybe just because they can get the care they need,” Marcozzi said. But ER patients with non-acute conditions contribute to overcrowding in emergency departments. (The latest study could not determine the quality of care received nor how ER usage contributes to people’s health outcomes.)

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But limiting ER use only to those with emergent conditions would be problematic. As Marcozzi points out, someone who goes to an emergency department with chest pain only to learn they have acid reflux wasn’t aware of that from the start. And patients aren’t very good judges of whether a condition is worthy of an ER visit. Instead, Marcozzi said that consumers and health-care professionals alike need to reconsider the role that emergency departments play in the medical system. “They have the wrong name — they should be called acute, unscheduled care departments,” he said.

In his view, emergency rooms are a model of customer-driven care — and efforts should be taken to improve coordination between primary care and specialty physicians and emergency departments. Cost aside, an emergency room visit could be more efficient time-wise than seeing multiple physicians to diagnose an ailment. Anyone from someone on Medicaid to a person with private insurance may choose to visit an emergency department because they can be sure that “comprehensive care will be provided in a timely fashion,” he said.