In addition to deductibles that many customers have said would bankrupt them in the event of an emergency, many ACA plans are extremely narrow networks that only include a small number of nearby physicians, specialists and hospitals.

There are more comprehensive plans, but they cost more. And at least one study by the Department of Health and Human Services has showed that the first priority of ACA customers is cost, not quality of coverage.

That’s one of the reasons that UnitedHealth struggled more than other insurers to turn a profit on the ACA marketplace. Its products typically were more expensive and provided broader networks than the low-cost plans that proved most popular.

There was an indication in 2015 that the trend was changing. Roughly 50 percent of marketplace customers chose the cheapest plan available, compared to two-thirds in 2014, the first year of the law’s implementation.

What is unclear, notes Sanger-Katz, is whether the Obamacare trend towards narrow networks is good or bad for patients. One recent study suggested that those with such plans spent less on health and were no more likely to experience negative health outcomes.

There are certainly some medical professionals who have voiced concern, however. Although uncompensated emergency room visits have declined since the law’s implementation, a survey of emergency room physicians showed that many reported ER visits from those with narrow network health plans, suggesting they were coming to the ER because they could not find a nearby physician covered by their insurance.