The effect of insurance on emergency room visits: An analysis of the 2006 Massachusetts health reform

This paper analyzes the impact of a major health reform in Massachusetts on emergency room (ER) visits. I exploit the variation in pre-reform uninsurance rates across counties to identify the causal effect of the reform on ER visits. My estimates imply that the reform reduced ER usage by between 5 and 8%, nearly all of which is accounted for by a reduction in non-urgent visits that could be treated in alternative settings. The reduction in emergency room visits is most pronounced during regular office hours when physician's offices are likely to be open. In contrast, I find no effect for non-preventable emergencies such as heart attacks. These estimates are consistent with a large causal effect of insurance on ER visits and imply that expanding insurance coverage could have a substantial impact on the efficiency of health services.