A decade ago, largely in response to widespread concerns that tired residents were making too many errors, the Accreditation Council for Graduate Medical Education enacted nationwide rules that limited the number of consecutive hours residents can work. Five years later, a review of the data suggested that, on average, the rules had failed to make our nation's teaching hospitals any safer. Proponents of the reforms argued that the rules had neither gone far enough nor been properly enforced. Accordingly, in 2011, first-year residents were limited even more—to sixteen-hour shifts, rather than the thirty hours previously allowed. Training programs scrambled to comply.