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 rate across counties to identify the causal effect of the reform on ER visits. My estimates imply that the reform reduced ER usage by about 8 percent, nearly all of which is accounted for by a reduction in non-urgent visits that could be treated in alternative settings. The reduction in non-urgent and primary-care treatable 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 usage and imply that expanding insurance coverage could have a substantial impact on the efficiency of health services.