1 Unit of Global Health, Department of Health Sciences, University Medical Center Groningen, Groningen, The Netherlands; Asc Academics, Groningen, The Netherlands. Electronic address: t.h.pham@umcg.nl.
2 Unit of Global Health, Department of Health Sciences, University Medical Center Groningen, Groningen, The Netherlands; Department of Economics, Econometrics & Finance, University of Groningen, Groningen, The Netherlands; Faculty of Management Sciences, Open University, Heerlen, The Netherlands.