The data are in, but debate rages: Are hospital readmission penalties a good idea?

A closely watched experiment in health care has unfolded over the last few years: Financial incentives for hospitals to reduce readmissions. It was a feature of the Affordable Care Act, and researchers are now assessing its impacts. But even as data have arrived, an impassioned argument has broken out among experts — looking at the same numbers, they have reached different conclusions about whether the policy is making Americans healthier.

And, underscoring that disagreement is a deeper one — about what kind of evidence is needed before a health policy is enacted on a national scale.

The policy, known as the , created financial penalties for hospitals whose readmissions exceed the national average for patients suffering from heart failure, heart attacks, and pneumonia. In recent years it has been expanded to include other conditions. Its aim was to encourage