Who Increases Emergency Department Use? New Insights from the Oregon Health Insurance Experiment

52 Pages Posted: 3 Feb 2022

See all articles by Augustine Denteh

Augustine Denteh

Tulane University - Department of Economics

Helge Liebert

University of Zurich

Multiple version iconThere are 2 versions of this paper

Date Written: January 18, 2022


We provide new insights into the finding that Medicaid increased emergency department (ED) use from the Oregon experiment. Using nonparametric causal machine learning methods, we find economically meaningful treatment effect heterogeneity in the impact of Medicaid coverage on ED use. The effect distribution is widely dispersed, with significant positive effects concentrated among high-use individuals. A small group—about 14% of participants—in the right tail with significant increases in ED use drives the overall effect. The remainder of the individualized treatment effects is either indistinguishable from zero or negative. The average treatment effect is not representative of the individualized treatment effect for most people. We identify four priority groups with large and statistically significant increases in ED use—men, prior SNAP participants, adults less than 50 years old, and those with pre-lottery ED use classified as primary care treatable. Our results point to an essential role of intensive margin effects—Medicaid increases utilization among those already accustomed to ED use and who use the emergency department for all types of care. We leverage the heterogeneous effects to estimate optimal assignment rules to prioritize insurance applications in similar expansions.

Funding Information: None to declare.

Declaration of Interests: None to declare.

Keywords: Medicaid, ED visit, effect heterogeneity, machine learning, efficient policy learning

JEL Classification: H75, I13, I38

Suggested Citation

Denteh, Augustine and Liebert, Helge, Who Increases Emergency Department Use? New Insights from the Oregon Health Insurance Experiment (January 18, 2022). Available at SSRN: https://ssrn.com/abstract=4012071 or http://dx.doi.org/10.2139/ssrn.4012071

Augustine Denteh (Contact Author)

Tulane University - Department of Economics ( email )

New Orleans, LA 70118
United States

Helge Liebert

University of Zurich ( email )

Rämistrasse 71
Zürich, CH-8006

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