Poster #79 - How Do Statutory Law and Administrative Regulations Determine Medicaid Eligibility

• In Event: Friday Poster Reception

Abstract

Introduction/Background

Medicaid’s modified adjusted gross income (MAGI) rules generally base eligibility on monthly income and household composition. Empirical studies often rely on annual measures, potentially misclassifying eligibility and obscuring enrollment responses.

Purpose/Research Question

This paper examines whether aligning measurement with program rules reveals enrollment discontinuities at 138 percent of the federal poverty line (FPL) and changes estimated Medicaid expansion effects.

Data

I use the 2013–2016 Survey of Income and Program Participation (SIPP) and Current Population Survey (CPS) observations covering the same period.

Research Design and Methods

Drawing on federal regulations and CMS guidance, I construct lowest monthly earnings (LME) using monthly earnings and MAGI household composition. In the CPS, I apply household composition and employment restrictions to better approximate monthly eligibility. I compare enrollment estimates across measures using regression discontinuity and difference-in-differences designs.

Results/Findings

Among childless adults in expansion states, estimated enrollment declines at the threshold are 5.7 percentage points in the SIPP and 6–9 percentage points in the CPS. Difference-in-differences estimates indicate larger expansion effects among adults classified below the threshold using LME than annual income. Households with LME near 138 percent of the FPL have average annual incomes of approximately 200–220 percent.

Conclusion/Implications

Aligning survey measures with monthly eligibility rules reveals enrollment patterns obscured by annual measures and helps reconcile Medicaid coverage above conventional annual-income thresholds. These findings highlight how eligibility measurement shapes estimates of Medicaid’s coverage effects.

Author

• Mingjian Li, University of Illinois, Chicago
  Presenting Author