What makes a hospital the 'best'?

U.S. News & World Report recently published its annual “Best Hospitals” issue, which the magazine claims is the “global authority in hospital rankings.” That may be no exaggeration, given the more than two million Google results that appear with the search term “U.S. News hospital rankings” along with the flurry of self-congratulatory tweets posted and banners hung each year by the hospitals whose names appear at the top of the list.