Dropout rates increased among Michigan Medicaid enrollees when they had to pay premiums for coverage. That is the finding of a recent study by the National Bureau of Economic Research.

The study analyzed enrollee data between 2014 and 2016 and found the percentage of healthier people leaving Michigan’s Medicaid program increased from 25% to 28% in the six months after enrollment.

Since the expansion of Medicaid under the Affordable Care Act, states have sought increased flexibility from the Centers for Medicare and Medicaid Services on how they design their programs. As a condition of expanding Medicaid, several states including Michigan, Arkansas, Indiana, Iowa and Montana require enrollees to pay an increased share of their healthcare costs.

Michigan charges monthly premiums ranging from $12 to $29 for Medicaid enrollees with incomes at or above the poverty line.

The researchers found charging premiums could come with higher costs. As healthier people leave, those that remain in the program could be sicker and require more expensive care.

In Michigan, Medicaid enrollees cannot be removed from the program or denied care for failing to pay premiums, but money can be withheld from tax refunds or lottery winnings.