It's a truism that "we manage what we measure"—but for hospital leaders who want to "manage" their hospital's CMS star rating, it's been hard to know exactly what's being "measured" in the first place. The rating process, first established in 2016, has been largely opaque to providers. And for a system that's naturally going to attract skepticism, as any system picking "winners" and "losers" among hospitals would do, that opacity been a source of major controversy.