Author Contributions: Dr Shen had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Hsia, Shen.
Acquisition of data: Shen.
Analysis and interpretation of data: Hsia, Kellermann, Shen.
Drafting of the manuscript: Hsia.
Critical revision of the manuscript for important intellectual content: Kellermann, Shen.
Statistical analysis: Shen.
Obtained funding: Hsia, Shen.
Administrative, technical, or material support: Hsia, Kellermann.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Funding/Support: This publication was supported by NIH/NCRR/OD UCSF-CTSI grant KL2 RR024130 (R.Y.H.), the Robert Wood Johnson Foundation Physician Faculty Scholars (R.Y.H.), and the Robert Wood Johnson Foundation Changes in Health Care Financing and Organization initiative (grant 63974) (Y.S.).
Role of the Sponsor: The sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.
Disclaimer: The article contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health or the Robert Wood Johnson Foundation.
Additional Contributions: We especially thank Michael L. Callaham, MD (Department of Emergency Medicine, University of California, San Francisco), and Amy J. Markowitz, JD (University of California, San Francisco), for their very constructive suggestions and revisions in the preparation of the manuscript; Tanja Srebotnjak, PhD (Ecologic Institute, Berlin, Germany), for her assistance in the generation of the map in eFigure 2; and Tiffany Wang, BA (Department of Emergency Medicine, University of California, San Francisco), for her technical support. None received additional compensation other than university salary for their contributions, except for Dr Srebotnjak, who was compensated for her contribution.
This article was corrected for errors on June 7, 2011.