That helps explain why policy experts believe millions of children could lose coverage under the new plan. A December report by the Urban Institute, a nonpartisan think tank based in Washington, estimated a partial repeal of the ACA in the context of budget reconciliation would result in 4.4 million children losing coverage. The institute hasn’t yet released an estimate for the new plan. *

“When you pull back eligibility for Medicaid or CHIP, you do expect higher uninsurance among kids,” said Genevieve Kenney, the co-director of the institute’s Health Policy Center.

“The other thing that I always keep in mind when I’m studying children and their well-being is that how their parents are doing matters,” she added. “If the parents are going without care the they need—think about untreated depression. And think about the financial dimension of this, too. If parents now are experiencing much larger out-of-pocket costs associated with meeting their health-care needs, that adversely affects the budget for the family.”

In other words, just making sure that kids are eligible for coverage isn’t enough. They have to enroll. And insurance has to be affordable enough that paying for it doesn’t stretch families too thin. That’s why many policy experts are concerned about giving states the flexibility to implement cuts to Medicaid. Flexibility, in this case, could mean new enrollment caps, or rules about work requirements, or other measures that reduce participation in programs like Medicaid. Governors can’t implement Medicaid cuts without “direct cutbacks in the health-care that the 70 million Americans on Medicaid rely upon,” Alker wrote in a blog post.

Widespread insurance coverage actually drives down costs over time, Racine says, if you look at the opportunity cost associated with foregoing preventative care like vaccines, or delaying a doctor visit when something seems off, or relying on the emergency room in lieu of going to a primary care doctor.

“It’s not so much the cost of the intervention, it’s the cost of the absence of the intervention you have to compare it to,” said Andrew D. Racine, a pediatrics professor at the Albert Einstein College of Medicine and a researcher at the National Bureau of Economic Research. “If you vaccinate little Johnny, not only are you protecting little Johnny but you’re protecting his grandmother because he cannot communicate that disease to her. So she gets a benefit that she doesn’t have to pay for—and society doesn’t have to pay for. Then you look at the benefits of little Johnny getting covered by Medicaid down the line. He is more likely to do well in school, to graduate, to go to college, to have a higher income.”

There’s abundant evidence to support the idea that Medicaid has significant downstream effect on its enrollees’ lives. Medicaid was founded in 1965, and has been studied closely ever since. The National Bureau of Economic Research has found, for instance, a direct connection between expanding health insurance coverage for low-income children and an increased rate of high school and college completion.