Record check studies show that survey estimates of enrollment in government-assistance programs tend to be lower than those compiled from records used for program administration, and this undercount is especially apparent for Medicaid. Studies specific to Medicaid point to false-negative reporting about enrollees in surveys as the main explanation, however their results differ with respect to findings about the level of this response error. It is unclear how much study differences owe to genuine discrepancies in how different surveys measure Medicaid versus being artifacts of different methods for measuring the undercount. This study helps to clarify this question by comparing the results of using one set of variables, derived from the same administrative database, to separately model Medicaid misreport in two different surveys: the Current Population Survey Annual Social and Economic Supplement (CPS ASEC) and in the National Health Interview Survey (NHIS), both fielded in 2001. 

Results suggest that survey design has an important effect on Medicaid reporting, and most notably that differences in reference period are enough to explain differences in the probability of false-negative reporting in CPS and NHIS, controlling for sample differences. Results corroborate findings that the probability of misreport depends on particular characteristics of the enrollee, and also add evidence suggesting that many enrollee-related predictors of misreport may be quite robust to some differences in survey design. To learn more about the relationships between specific features of survey design and false negative reporting, these results imply that it would be fruitful to look closer at the effect of having private insurance (at the same time as Medicaid) and of being enrolled in other assistance programs.