Many in the Obama administration bemoan the fact that 19 states have opted out of Medicaid expansion under the Affordable Care Act. But the program’s patchwork implementation might have helped prove the law’s value, according to the New York Times.

In states that chose Medicaid expansion (such as Arkansas and Kentucky), people are turning out to be healthier and more willing to seek care than in states where Medicaid expansion was eschewed (such as Texas). People in Arkansas and Kentucky were 5 percent more likely to say they were in “excellent” health in 2015 than people in Texas.  

There could be other factors confounding the results, researchers pointed out. This study doesn’t prove direct causation, and policy makers and physicians alike will need more information after the law has been in effect for several years.

But seeing increasing numbers of people who are not worried about medical costs or who have a regular doctor in expansion states is a good sign for the ACA’s champions.

Check out the New York Times to see why this method of asking people about their own health might be the best way to measure the ACA’s effectiveness.