The Effect of Health Insurance on Mortality: What Can We Learn from the Affordable Care Act Coverage Expansions?
53 Pages Posted: 7 May 2019
Date Written: April 8, 2019
A large literature examines the effect of health insurance on mortality. We add to this literature by emphasizing two challenges in using quasi-experimental variation provided by the Affordable Care Act (ACA) coverage expansions to study mortality. The first is non-parallel pre-treatment trends. Mortality was rising in Medicaid non-expansion relative to expansion states prior to Medicaid expansion, making it difficult to estimate the effect of insurance using difference-in-differences (DD). We use various DD, triple difference, age-discontinuity (at Medicare age) and synthetic control approaches, but are unable to find a research design that satisfactorily addresses this concern. Our estimates are not statistically significant at conventional levels, and are imprecise enough to be consistent with both no effect and a large effect of ACA expansion on overall mortality for non-elderly adults over the first three post-ACA years. Thus, our results should not be interpreted as evidence that health insurance has no effect on mortality for this age group, especially in light of the literature documenting greater health care use as a result of the ACA.
Second, we provide a simulation-based power analysis, showing that even the nationwide natural experiment provided by the ACA is underpowered to detect plausibly sized mortality effects in available datasets, and discuss data element and sample size needs for the literature to advance. Our power analysis approach, which applies simulated pseudo-shocks to actual data in the pre-treatment period, is broadly applicable to other natural-experiment studies. Such analyses can reduce the likelihood of false positives and increase the validity of reported results.
The Online Appendix for this paper is available on SSRN at: https://ssrn.com/abstract= 3368192.
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