Gavin Yamey1, Marco Schäferhoff2, Kaci Kennedy3. 1. Center for Policy Impact in Global Health, Duke Global Health Institute, Duke University, Durham, NC 27708, USA. Electronic address: gavin.yamey@duke.edu. 2. Open Consultants, Berlin, Germany. 3. Center for Policy Impact in Global Health, Duke Global Health Institute, Duke University, Durham, NC 27708, USA.