1 Department of Economics, University of Göttingen, Germany; Department of Global Health and Population, Harvard School of Public Health, Harvard University, Boston, MA, USA.
2 UNAIDS, Geneva, Switzerland.
3 ETH, Zürich, Switzerland.
4 Department of Global Health and Population, Harvard School of Public Health, Harvard University, Boston, MA, USA; Wellcome Trust Africa Centre for Heath and Population Studies, University of KwaZulu-Natal, South Africa. Electronic address: [email protected].