About the Authors

Su-Ting T Li

To whom correspondence should be addressed. E-mail: su-ting.li@ucdmc.ucdavis.edu

Affiliation Department of Pediatrics, University of California Davis, Sacramento, California, United States of America

David C Grossman

Affiliations Department of Preventive Care, Group Health Cooperative, Seattle, Washington, United States of America , Center for Health Studies, Group Health Cooperative, Seattle, Washington, United States of America , Department of Health Services, University of Washington, Seattle, Washington, United States of America , Department of Pediatrics, University of Washington, Seattle, Washington, United States of America

Peter Cummings

Affiliation Department of Epidemiology, University of Washington, Seattle, Washington, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

STL and DCG designed the study and analyzed the data. STL, DCG, and PC contributed to writing the paper.