Free-for-all: Does crowding impact outcomes because hospital emergency departments do not prioritise effectively?

Unexpected peaks in volumes of attendances at hospital emergency departments (EDs) have been found to affect waiting times, care intensity and outcomes. We ask whether these effects of ED crowding on patients are caused by poor clinical prioritisation or a quality-quantity trade-off generated by a binding capacity constraint. We study the effects of crowding created by lower-severity patients on the outcomes of7 approximately 13 million higher-severity patients attending 140 public EDs in England between April 2016 and March 2017. Our identification approach relies on high-dimensional fixed effects to account for planned capacity. Unexpected demand from low-severity patients has very limited effects on the care provided to higher-severity patients throughout their entire pathway in ED. Crowding effects materialise only at very high levels of avoidable demand, when resource constraints bind. These effects are smaller than those caused by crowding induced by higher-severity patients, suggesting efficient prioritisation of incoming patients in EDs.