Author Contributions: Dr McWilliams 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: McWilliams.
Acquisition of data: McWilliams.
Analysis and interpretation of data: McWilliams, Zaslavsky, Huskamp.
Drafting of the manuscript: McWilliams.
Critical revision of the manuscript for important intellectual content: McWilliams, Zaslavsky, Huskamp.
Statistical analysis: McWilliams, Zaslavsky.
Obtained funding: McWilliams.
Administrative, technical, or material support: McWilliams, Huskamp.
Study supervision: Huskamp.
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 study was supported by grants from the Doris Duke Charitable Foundation (Clinical Scientist Development Award 2010053, Dr McWilliams), the William F. Milton Fund (Dr McWilliams), and a Robert Wood Johnson Foundation Investigator Award in Health Policy Research (Dr Huskamp).
Role of the Sponsor: The Doris Duke Charitable Foundation, William F. Milton Fund, and Robert Wood Johnson Foundation had no role in the design and conduct of the study; the collection, management, analysis, and interpretation of the data; or the preparation, review, and approval of the manuscript.
Additional Contributions: We thank Pasha Hamed, MA (Department of Health Care Policy, Harvard Medical School), for statistical programming supported by grants from the Doris Duke Charitable Foundation (Clinical Scientist Development Award 2010053, Dr McWilliams) and the William F. Milton Fund (Dr McWilliams).