1. Research Associate, The Water Institute, Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Correspondence:
2. Senior Lecturer, Department of Community Medicine, College of Medicine, University of Ibadan, University College Hospital, Ibadan, Nigeria
3. Statisticien Démographe, Conseiller du Directeur Général, l’Institut National de la Statistique du Niger, Niamey, Niger
4. Ingénieur Statisticien Economiste, Directeur des Enquêtes et des Recensements, l’Institut National de la Statistique du Niger, Niamey, Niger
5. Lecturer, Institut Supérieur des Sciences de la Population, University of Ouagadougou, Ouagadougou, Burkina Faso
6. Senior Lecturer, Department of Statistics, University of the Western Cape, Cape Town, South Africa
7. Professor, The Water Institute, Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA