Author Contributions: Dr Fang 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: Dickler, Fang, Korn.
Analysis and interpretation of data: Dickler, Fang, Heinig, Johnson, Korn.
Drafting of the manuscript: Dickler, Heinig, Korn.
Critical revision of the manuscript for important intellectual content: Dickler, Fang, Heinig, Johnson, Korn.
Statistical analysis: Fang, Johnson.
Administrative, technical, or material support: Heinig, Korn.
Study supervision: Korn.
Financial Disclosures: None reported.
Funding/Support: Data used in this study have been made available under the National Institutes of Health Contract N01-OD-3-1015 with the Association of American Medical Colleges.
Acknowledgment: We thank Hershel Alexander, PhD, of the Association of American Medical Colleges for his collegiality and assistance in gaining access to Association of American Medical Colleges data resources and systems used in this study, and Scott Zeger, PhD, professor and chair in biostatistics at the Johns Hopkins University School of Public Health for advice and guidance on statistical methods and permitting us to recruit his student (Ms Johnson) into this effort. The individuals listed in this acknowledgment were not compensated for their contributions.