Medicaid expansion and the Medicaid undercount in the American Community Survey

Michel Boudreaux, James M. Noon, Brett Fried, Joanne Pascale

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Objective: To measure discordance between aggregate estimates of means-tested coverage from the American Community Survey (ACS) and administrative counts and examine the association of discordance with ACA Medicaid expansion. Data Sources: 2010-2016 ACS and counts of Medicaid and Children's Health Insurance Program enrollment from the Centers for Medicare & Medicaid Services. Study Design: State-by-year counts of means-tested coverage from the ACS were compared to administrative counts using percentage differences. Discordance was compared for states that did and did not adopt expansion using difference-in-differences. We then contrasted the effect of expansion on means-tested coverage estimated from the ACS with results from administrative data. Data Collection/Extraction: Survey and administrative data. Principal Findings: One year before expansion there was a 0.8 and 4 percent overcount in expansion and nonexpansion states, respectively. By 2016, there was a 10.64 percent undercount in expansion states vs a 0.02 percent undercount in nonexpansion states. The ACS suggests that expansion increased means-tested coverage in the full population by three percentage points, relative to five percentage points suggested by administrative records. Conclusions: Discordance between the ACS and administrative records has increased over time. The ACS underestimates the impact of Medicaid expansion, relative to administrative counts.

Original languageEnglish (US)
Pages (from-to)1263-1272
Number of pages10
JournalHealth services research
Issue number6
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
Joint Acknowledgment/Disclosure Statement: This research was conducted when some coauthors were under the employment of the U.S. Census Bureau. This article is released to inform interested parties of research and to encourage discussion. Any opinions and conclusions expressed herein are those of the author(s) and do not necessarily represent the views of the U.S. Census Bureau. All results have been reviewed and cleared by the Census Bureau Disclosure Review Board CBDRB-FY19-284 to ensure that no confidential information is disclosed.

Publisher Copyright:
© Health Research and Educational Trust


  • American Community Survey
  • Medicaid


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