Swamped: Emergency Department Crowding and Patient Mortality.

U.S. emergency departments are experiencing extreme levels of crowding. This study estimates the impact of emergency department crowding on patient mortality. Identification relies on the abrupt crowding shocks felt by "old" emergency departments at the time a new emergency department opens nearby. Using death records linked to hospital administrative records, I find that a 10% alleviation of emergency department patient volume significantly lowers the average patient's chance of mortality. Improvements appear to be realized both inside the hospital and after the patient has left.