Redesign of the Medicare Current Beneficiary Survey Sample

1. Introduction The Medicare Current Beneficiary Survey (MCBS) conducted by the Centers for Medicare and Medicaid Services (CMS), Department of Health and Human Services, is a continuous sample survey of Medicare beneficiaries residing in the United States and Puerto Rico. The MCBS collects data on access to health care, health status, source of care, health care utilization and costs, satisfaction with health care, and other health-related topics representative sample of Medicare beneficiaries (referred to as a " panel ") is selected for the MCBS each year using a stratified multistage probability sample design. The sample of first-stage or primary sampling units (PSUs), which includes MSAs (metropolitan statistical areas) and groups of rural (nonMSA) counties, was designed and selected in 1991. Although new beneficiary samples are selected each year to supplement the original sample, the new samples are always selected from the same PSUs. Over time, the continued use of the original PSU sample has resulted in losses in both sampling precision and operational efficiency. In 2000, based on an evaluation of the existing PSU sample, a decision was made to reselect the PSUs. This paper summarizes some of the analyses leading to that decision and describes the procedures used to update and select the new MCBS PSU sample. 2. The MCBS Sample Design The MCBS employs a stratified multistage probability sample with three stages of selection. The first stage involved the selection of PSUs consisting of MSAs and groups of rural counties. The PSUs were selected with probabilities proportionate to 1980 population within strata defined by Census region, metropolitan status, and selected PSU-level socioeconomic characteristics. Two PSUs were selected per stratum. The second sampling stage consisted of the selection of ZIP Code areas within each sampled PSU. To facilitate linking with available county-level data, the second-stage sampling unit was defined to be the part of the ZIP Code area that was physically contained within a given county. In other words, ZIP Code areas that crossed county borders were subdivided by county into separate units called " ZIP fragments. " For sampling purposes, small ZIP fragments were combined into clusters where necessary to ensure that each ZIP cluster would provide a reasonable workload for interviewers if selected for the sample. At the third and final stage of selection, beneficiaries within the sampled ZIP clusters were stratified by age and subsampled at rates designed to yield self-weighting (equal probability) samples of beneficiaries …