Detailed analysis of state and national data demonstrates that enrollment in Medicaid-Managed Care does not contribute to the Medicaid Undercount, despite conflicting results from previous studies. Improved survey techniques are therefore necessary to accurately determine the number of American uninsured.
This study aimed to resolve a conflict in the literature on whether and how Medicaid-Managed Care (MMC) affects the Medicaid Undercount. Medicaid Undercount is the phenomenon in which general population surveys count fewer Medicaid enrollees than administrative data; MMC is a potential cause of enrollment underreporting. The authors mimicked the analysis techniques of earlier studies using aggregate California-only data, aggregate national data (analysis lacking a fixed-effect term), and both California and national individual-level data. This new analysis demonstrates that the results of earlier studies indicating that MMC contributes to Medicaid Undercount are not robust.
It is therefore unlikely that increased MMC enrollment explains the increased Medicaid Undercount. The authors hypothesize that with Medicaid and CHIP serving higher income brackets, those with higher income may misreport their enrollment. Further study is needed to determine the causes of Medicaid Undercount and to develop ways to accurately measure the number of uninsured Americans.