Author Contributions: Study concept and design: Samal and Hicks. Acquisition of data: Samal. Analysis and interpretation of data: Samal and Lipsitz. Drafting of the manuscript: Samal and Lipsitz. Critical revision of the manuscript for important intellectual content: Lipsitz and Hicks. Statistical analysis: Samal and Lipsitz. Study supervision: Hicks.
Financial Disclosure: Dr Hicks is a Board Member of Health Resources in Action and a scientific advisory board member to the Health Management Corporation.
Additional Contributions: Jeffrey A. Linder, MD, MPH, provided advice on NAMCS and Shimon Shaykevich, MS, assisted in data management.
This article was corrected for errors in the Figure on February 1, 2012.