Most health care plans ask that you spend some money out of your pocket whenever you use the health care system. This is known as cost-sharing, and it exists because research has shown us that people are, in general, less likely to spend their own money than someone else’s. Cost-sharing works its way into insurance today through co-pays, deductibles and co-insurance.

Cost-sharing works for most people, because most people are healthy. Healthy people who use health care are often doing so inefficiently. They often don’t need the care they ask for, because they’re well. One way we use cost-sharing poorly, though, is that we apply it to all insurance beneficiaries equivalently. We treat them all the same, no matter how sick or healthy they are.

A study just published in JAMA Pediatrics looked at how children with asthma obtained care under different levels of cost-sharing, and how much stress their families were under financially because of their child’s illness. It’s important to understand that children with asthma, by definition, require care.