Author Contributions: Dr Landon 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: Landon, Schneider, Normand, Scholle, Epstein.
Acquisition of data: Landon, Scholle, Pawlson, Epstein.
Analysis and interpretation of data: Landon, Schneider, Normand, Scholle, Epstein.
Drafting of the manuscript: Landon, Schneider, Normand, Scholle.
Critical revision of the manuscript for important intellectual content: Schneider, Normand, Pawlson, Epstein.
Statistical analysis: Normand.
Obtained funding: Landon, Schneider, Normand, Epstein.
Administrative, technical, or material support: Normand, Epstein.
Study supervision: Epstein.
Financial Disclosures: None reported.
Funding/Support: This work was supported by grant 043782 from the Robert Wood Johnson Foundation (Dr Epstein).
Role of the Sponsor: The Robert Wood Johnson Foundation had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Disclaimer: Drs Pawlson and Scholle are employees of the National Committee for Quality Assurance.
Additional Contributions: We are indebted to Charlene Hsuan, BS, Department of Health Policy and Management, Harvard School of Public Health, for research assistance; Lin Ding, PhD, for assistance with expert statistical programming, and Eva Tomczyk, BA, Department of Health Care Policy, Harvard Medical School, for assistance with manuscript preparation. Ms Hsuan is now enrolled in the New York University School of Law and Ms Tomczyk is now with the Department of Social Medicine. The individuals named in this acknowledgment were paid employees of their respective institutions at the time of this study.