1. Department of Political Science and International Relations, School of Social Sciences, University of Geneva, 1211 Geneva, Switzerland
2. Department of Population, Family and Reproductive Health, School of Public Health, University of Medical Sciences (UNIMED), Ondo City PMB 536, Nigeria
3. Department of Demography and Social Statistics, Federal University, Oye-Ekiti PMB 373, Nigeria
4. Demography and Population Studies Programme, School of Public Health and Social Sciences, University of the Witwatersrand, Private Bag 3, Wits, Johannesburg 2050, South Africa