Medicaid Undercount Project (SNACC)

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Census.govPopulation SNACC Main Description of Phases

Description of Phases

Phase I: Overview of Medicare and Medicaid Files
In Phase I, a national database of health insurance information is created and evaluated. The CMS Medicaid Statistical Information System (MSIS) files are merged with the CMS Medicare (EDB) files. We assess our ability to accurately merge the input files and compare the characteristics of the individuals in the database to expectations based on Medicaid eligibility rules and characteristics of the U.S. population.

Phase II: Comparing MSIS and the CPS ASEC, 2001-2002
In Phase II, the Medicaid Analytic Extract (MAX), MSIS, the Current Population Survey Annual Social and Economic Supplement (CPS ASEC), the Person Characteristic File (PCF), and the Master Address File Auxiliary Reference File (MAF-ARF) are used to determine matches (and non-matches) between the MSIS and CPS ASEC. Matched records are supplemented with information from the MAX and discrepancies between MSIS records of enrollment and CPS reports of Medicaid coverage are analyzed. The MAF-ARF and PCF are used to augment the analysis.

Phase III: Refinements in MSIS CPS ASEC Comparison
In Phase III, data from the state MSIS files, CPS ASEC, 2001 American Community Survey Supplemental Survey (ACS/SS01), MAX, and Master Address File (MAF) are used. Collaborating with CMS, Census Bureau acquired state MSIS files to enhance and evaluate the survey-administrative record matching process. Frame coverage is analyzed to determine if frame differences (i.e., incomplete identification of individuals) affect the substantive conclusions of the analysis.

Phase IV: Comparing MSIS and NHIS, 2001-2002
In Phase IV, the Phase II process is replicated using NHIS data instead of CPS ASEC data. In addition to providing explanations for discrepancies between the national NHIS and MSIS, Phase IV results allow the examination of how survey design and implementation affect the quality of the resulting survey data and the estimates derived from it.

Phase V: Comparing MSIS and the CPS ASEC, 2003-2004
Phase V is a repeat of Phase II with later years of the CPS. The intent of this Phase is to see if the discrepancy measured and explained in Phase II changes noticeably in the size or the relationship to explanatory factors from 2000 and 2001 to 2002 and 2003.

Phase VI: Comparing MSIS and MEPS
Phase VI replicates the Phase II process but uses the calendar year 2003 Medical Expenditure Panel Survey (MEPS) data. The intent of Phase VI is to determine how the MEPS estimate of the number of Medicaid enrollees compare to the count from National MSIS as well as to determine factors associated with false-negative response about Medicaid in MEPS.

Source: U.S. Census Bureau | Medicaid Undercount Project |  Last Revised: September 03, 2009