An Overview of New CMS Data on the Number of Adults Enrolled in the ACA Medicaid Expansion

New preliminary data from the Medicaid Budget and Expenditure System (MBES) released by the Centers for Medicare and Medicaid Services (CMS) details for the first time the number of adults enrolled in Medicaid under the new Affordable Care Act (ACA) Medicaid expansion category. The data show that as of March 2014, among 48 states reporting data, 4.8 million adults out of the total 54.1 million individuals enrolled in Medicaid were in the ACA Medicaid expansion category. These data provide another element of Medicaid enrollment that differs from other enrollment data released from CMS as part of its Medicaid and CHIP Performance Indicator Project, which provide point-in-time Medicaid and CHIP enrollment data to support program management and oversight. These two data sets are not comparable; they have different purposes and include different populations. This issue brief provides an overview of the new data as well as how it differs from the Performance Indicator data.