Study concept and design: Fenelon, Chen.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Fenelon.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Fenelon, Chen.
Administrative, technical, or material support: Fenelon.
Study supervision: Fenelon.
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 the US Centers for Disease Control and Prevention.
Role of the Funder/Sponsor: The US Centers for Disease Control and Prevention supported the staff responsible for the design and conduct of the study; in the collection, analysis, and interpretation of the data; in the preparation, review, and approval of the manuscript; and in the decision to submit the manuscript for publication.
Disclaimer: The views expressed in this article are those of the authors and do not necessarily reflect the official position of the US Centers for Disease Control and Prevention.
Additional Contributions: We thank the National Center for Health Statistics for institutional support and to Robert Anderson, PhD (National Center for Health Statistics), Holly Hedegaard, MD, MSPH (National Center for Health Statistics), and John Wilmoth, PhD (University of California, Berkeley), for helpful comments on an earlier version of the manuscript, none of whom received compensation.