As managed care became popular, health care quality became an important aspect. The HMO Act in 1973 included a voluntary program of "federal qualification", which became popular, but over time this role was largely taken over by the National Committee for Quality Assurance (NCQA), which began accrediting plans in 1991. Accreditation by the NCQA is often expected or require by employers. The Healthcare Effectiveness Data and Information Set (HEDIS) is a prominent set of measurements and reporting on it is often mandated by states as well as Medicare; as of 2017, HEDIS data was collected for plans covering 81% of the insured.