An Examination of the Medicaid Undercount in the Current Population Survey: Preliminary Results from Record Linking

Abstract

Objective. To assess reasons why survey estimates of Medicaid enrollment are 43 percent lower than raw Medicaid program enrollment counts (i.e., “Medicaid undercount”). Data Sources. Linked 2000–2002 Medicaid Statistical Information System (MSIS) and the 2001–2002 Current Population Survey (CPS). Data Collection Methods. Centers for Medicare and Medicaid Services provided the Census Bureau with its MSIS file. The Census Bureau linked the MSIS to the CPS data within its secure data analysis facilities. Study Design. We analyzed how often Medicaid enrollees incorrectly answer the CPS health insurance item and imperfect concept alignment (e.g., inclusion in the MSIS of people who are not included in the CPS sample frame and people who were enrolled in Medicaid in more than one state during the year). Principal Findings. The extent to which the Medicaid enrollee data were adjusted for imperfect concept alignment reduces the raw Medicaid undercount considerably (by 12 percentage points). However, survey response errors play an even larger role with 43 percent of Medicaid enrollees answering the CPS as though they were not enrolled and 17 percent reported being uninsured. Conclusions. The CPS is widely used for health policy analysis but is a poor measure of Medicaid enrollment at any time during the year because many people who are enrolled in Medicaid fail to report it and may be incorrectly coded as being uninsured. This discrepancy should be considered when using the CPS for policy research.

CHIP Reporting in the CPS

“…Specifically, we link individual-level CPS data to corresponding individual-level administrative data from the Centers for Medicare & Medicaid Services' (CMS) Medicaid Statistical Information System (MSIS). Earlier studies have shown that CPS Medicaid reporting has a substantial number of errors associated with it (Davern, Baugh, Call, Cox, & Klerman, 2009;Klerman, Davern, Call, Lynch, & Ringel, 2009). In this paper, we examine CHIP reporting in the CPS and we show that CPS CHIP reporting is far less accurate than Medicaid reporting, calling into question the value of the CHIP responses in the CPS for researching the CHIP program.…”

“…The CPS Annual Social and Economic supplement is fielded annually and is not a longitudinal dataset, so MSIS data could simply be matched with the CPS and appended together. The U.S. Census Bureau (2007Bureau ( , 2008 and Davern et al (2009) In brief, CMS provided the Census Bureau with extracts of its MSIS file containing state monthly individual-level data on Medicaid coverage. In its secure data facility and with appropriate protections of privacy, confidentiality, and data security, the Census Bureau matched all individual-level data from the MSIS file to the corresponding CPS records.…”

Increase In Federal Match Associated With Significant Gains In Coverage For Children Through Medicaid And CHIP

“…We refer to Medicaid and CHIP together as Medicaid through the remainder of this article.We chose to combine the programs because this is how the data are typically reported and because previous studies of Current Population Survey data have suggested that CHIP enrollees might incorrectly indicate in the survey that Medicaid was their primary source of health insurance coverage. 7 The proportion of children living in poverty is related to but distinct from state-level per capita income used to set the federal match rates. The Current Population Survey was also the source of data regarding elderly people enrolled in Medicaid in each state during the study period.…”

Simulation Modeling of Health Care Policy

“…Studies comparing self-reported Medicaid status in the CPS with administrative counts find that respondents in the CPS underreport participation in Medicaid, which artificially inflates the number of uninsured (9); however, misreporting occurs in all directions, and some Medicaid enrollees report that they are privately insured, whereas some nonenrollees report Medicaid coverage (35).…”