The Impact of Differing COVID-19 Mitigation Policies: Three Natural Experiments

This paper presents a comparison of the COVID-19 infections between a select pair of neighboring states and their border county regions where the policies of the Non-Pharmaceutical Interventions (NPI) such as Lockdown/Stay-at-Home differ. These analyses use a Difference-in-Differences (Diff-in Diff) model to test the effectiveness of NPI in mitigating COVID-19 infections at the state and border county regions between these states. The counties are in the states on the Iowa and Illinois border, the Dakotas (North and South) and Minnesota border and the Arkansas and Mississippi border. In each case the policies on each side of the border differ and the border is clearly designated by a river separation. Based on the Diff-in-Diff model output, state policies appear to make a significant difference in some of these specific border regions, at least early in the pandemic (April-June 2020). State level results are mixed reflecting spatial heterogeneity across the inter-state system.