Health Outcomes SurveyThe Medicare Health Outcomes Survey (HOS) is the first patient-reported outcomes measure used in Medicare managed care. The goal of the Medicare HOS is to gather valid, reliable, and clinically meaningful health status data from the Medicare Advantage (MA) program to use in quality improvement activities, pay for performance, program oversight, public reporting, and to improve health. All managed care organizations with Medicare contracts must participate. The HOS is administered annually to a random sample of Medicare beneficiaries drawn from each participating MA plan and surveyed in the spring (i.e., a baseline survey is administered to a new cohort, or group, each year). Two years later, these same respondents are surveyed again (i.e., follow up measurement). The baseline sample size is twelve hundred. Cohort 1 was surveyed in 1998 and was re-surveyed in 2000. During the 2016 HOS administration, Cohort 19 was surveyed (baseline) and Cohort 17 re-surveyed (follow-up).