Protocol - Evaluating the Effect of ACA Medicaid Expansion on Mortality During the COVID-19 Pandemic Using County-level Matching.

States are able to choose whether to expand Medicaid as part of the Affordable Care Act (ACA); thus it is of interest to understand the impact of this policy choice. In this protocol, we outline a study on the impact of Medicaid expansion as part of the ACA on mortality during the COVID-19 pandemic in the United States. County-level matching using full, optimal matching with a propensity score model is used to estimate causal effects in this observational study. Due to the provisional nature of mortality data in 2020 as reported by the CDC, we outline a modified aligned rank test to account for censored data as well as reporting lags for different states. We aim to make connections between statistical and ethnographic methodologies by particularly examining adjacent counties and similar counties that are in the same region of the US and in vastly different regions of the US. Finally, we aim to add to the growing literature about the effect of ACA Medicaid expansion on mortality by calculating effects, disaggregating by race.