California Hospitals Serving Large Minority Populations Were More Likely Than Others To Employ Ambulance Diversion

Published in: Health Affairs, Vol. 31, No. 8, Aug. 2012, p. 1767-1776

Posted on on August 01, 2012

by Renee Y. Hsia, Steven M. Asch, Robert Weiss, David Zingmond, Li-Jung Liang, Weijuan Han, Heather McCreath, Benjamin C. Sun

Research Question

  1. Does emergency department crowding disproportionately affect minority populations, aggravating existing health care disparities?

It is well documented that racial and ethnic minority populations disproportionately use hospital emergency departments for safety-net care. But what is not known is whether emergency department crowding is disproportionately affecting minority populations and potentially aggravating existing health care disparities, including poorer outcomes for minorities. We examined ambulance diversion, a proxy measure for crowding, at 202 California hospitals. We found that hospitals serving large minority populations were more likely to divert ambulances than were hospitals with a lower proportion of minorities, even when controlling for hospital ownership, emergency department capacity, and other hospital demographic and structural factors. These findings suggest that establishing more-uniform criteria to regulate diversion may help reduce disparities in access to emergency care.

Key Findings

  • Hospitals serving large minority populations were more likely to divert ambulances.
  • Disparities arise from “upstream” causes before patients reach their hospital destination, such as poor management of patient flow.
  • Minority populations may live in areas where there is a fundamental mismatch in supply and demand of emergency department services.


  • Policies to regulate ambulance diversion may help providers and hospital administrators reduce diversion and its disproportional effect on minority populations.

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