For several years, there has been debate whether CMS's readmissions penalties improve or hurt healthcare. The top line purpose is obvious: to discourage arbitrary readmissions ($15,000,ka-ching!), and to encourage effort in thoughtful aftercare to improve health and make readmissions recidivism lower.
The downside is discouraging medically necessary readmissions of complex and unstable patients.
This story is featured in a long article today in New York Times by Paul Span (here). NYT even notes the issue is not "new news" but pulls the issue together for readers.
JAMA December 2018, Wadhera et al.
The entry point is the Wadhera et al. studied, published in JAMA on December 25, 2018, associating readmissions reduction with increased mortality (here). An earlier article in JAMA had proposed that 60% of the change in readmissions figures were due to coding-of-severity changes (here).
In contrast, a June 2018 government MedPAC report (summarized in Circulation by Khera & Krumholz) didn't find an adverse effect of the readmissions policy (here in summary, here in original which is 32 pages of literature summary plus new analyses.)
Some additional articles on readmissions and unintended consequences here, here, here. For CMS Hospital Compare, where readmissions rates can be looked up, here.