1. Department of Health Services Policy and Management, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina.
2. Department of Health Policy and Management, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
3. Institute of Gerontology and Department of Economics, Wayne State University, Detroit, Michigan.
4. Division of General Medicine and Clinical Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.