1. Department of Health Management and Policy, University of Michigan School of Public Health, Ann Arbor, MI 48109, USA
2. Sanford School of Public Policy, Duke University, Durham, NC 27708, USA
3. Department of Economics, Duke University, Durham, NC 27708, USA
4. Duke Global Health Institute, Duke University, Durham, NC 27708, USA
5. Duke Population Research Institute, Duke University, Durham, NC 27708, USA
6. Boston College School of Social Work, Boston, MA 02467, USA
7. Department of Medicine, Duke University School of Medicine, Durham, NC 27708, USA
8. Moi University School of Public Health, College of Health Sciences, Eldoret, Kenya