A. Overview of MCBS

The Medicare Current Beneficiary Survey (MCBS) is conducted by the Office of Strategic Planning of the Centers for Medicare & Medicaid Services (CMS). It is a continuous, multipurpose survey of a nationally representative sample of the Medicare population, providing information on aged and disabled Medicare beneficiaries living in communities and long-term care facilities. The sample is selected from Medicare enrollment files, and sample persons are interviewed three times per year over a four-year period. Sample data are collected through computer-assisted personal interviews of the beneficiary or a proxy respondent if the sample person is not available for the interview. Survey questionnaires are tailored to the residence of the sample person—community or long-term care facility. If the sample person moves from one setting to the other during the period covered by an interview, a separate interview is administered for the time spent in each setting. As a consequence, beneficiaries are followed continuously over time regardless of where they live.

The primary goal of the survey is to collect comprehensive information on all medical services used by Medicare beneficiaries, sources of payment, health insurance coverage, and socioeconomic and demographic characteristics of the population. These data are used by the Office of Strategic Planning and the Office of the Actuary to support a host of activities related to the administration of the Medicare Program (health insurance for the aged and disabled) and the Medicaid Program (Federal grants to states for medical assistance programs). CMS also uses the data to evaluate the Medicare and Medicaid programs and to assess the financial impact of programmatic change on beneficiaries and the Medicare trust fund.

Two public use files (PUFs) are created for each calendar year of data collected in the MCBS: Access to Care and Cost and Use. Access to Care files are made available to the public about one year after the close of field work for the fall interview period (September-December). These PUFs contain the "always enrolled" segment of the Medicare population; i.e., individuals who were enrolled in Medicare Part A or Part B as of January 1 of the year of data collection and alive at the time of the fall interview. They exclude beneficiaries who enrolled in Medicare during the year, and beneficiaries who died before they could be interviewed in the fall round.

Access to Care files contain a mix of Medicare program data from administrative file and survey data from the fall round of interviews. The program data include summaries of Medicare-covered health care use and expenditures for the year. The survey-reported data include information from the fall round of interviews on health insurance coverage, health status and functioning, and access to and satisfaction with care. These PUFs are most appropriate for users interested in analyzing the continuously enrolled population and its use of Medicare-covered services. The files also contain longitudinal weights that can be used to track cohorts of Medicare beneficiaries over time (two, three or four years).

Cost and Use files are released about two years after the close of field work for the calendar year. They contain a nationally representative sample of "ever enrolled" Medicare beneficiaries, i.e., all persons who were in the program at any time during the calendar year. The data include survey-reported information on health care use, Medicare claims data for unreported services, and administrative data such as Medicaid buy-in status and Medicare managed care plan enrollment.

Health care expenditures in the Cost and Use files are created through an elaborate set of procedures to reconcile Medicare claims data and survey-reported events and to impute for missing information on sources and amounts of payment. As a result, Cost and Use files provide a more comprehensive picture of health care expenditures by Medicare enrollees than would be available from either the administrative data or the survey-reported events. They contain information on all services used by Medicare beneficiaries during the year including health care not covered by Medicare, and the sample is representative of the entire Medicare population. These files are most appropriate for analyses requiring all Medicare beneficiaries or expenditures on all types of health care.

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