It was a well-intended policy. Almost all parties agree on that much.

A decade ago, when Medicare beneficiaries were discharged from hospitals, one in five returned within a month.

Older people faced the risks of hospitalization all over again: infections, deconditioning, delirium, subsequent nursing home stays. And preventable readmissions were costing Medicare a bundle.

So the Affordable Care Act incorporated something called the Hospital Readmissions Reduction Program, which focused on three serious ailments with high readmission rates: heart failure, heart attacks and pneumonia.

The A.C.A. penalized hospitals — withholding up to three percent of Medicare payments — when readmissions within 30 days exceeded national averages.