Data Characterization of Medicaid: Legacy and New Data Formats in the CMS Virtual Research Data Center

Medicaid is a significant health insurance plan providing healthcare coverage to up to a third of the population of the United Sates. We describe two different formats of Medicaid data within Center for Medicare and Medicaid Services Virtual Research Data Center. We analyze record length, age and enrollment justification among patients for both data formats. As of December 2016, the total size of Medicaid population available from CMS is 92,953,389; 45% of patients are aged 0 to 18, 26.6% are aged 19-35 and 23.2% are aged 36-64. In terms of Medicaid eligibility, 35.6% qualify due to (child) age and 26.8% qualify due to income. We also compare the volume of Medicaid to Medicare for year 2016. We conclude that Medicaid data includes patients with significant record lengths and relatively well documented enrollment justification, which are high value assets for data reuse researchers that are willing to balance known data limitations with careful analysis design and interpretation.