Authors | countries | years | percentages |
Ugwu [16] Fabamwo [7] Akyuz [3] Lampiao [9] Okwelogu [12] Bello [5] Our study | Cameroun Nigéria Turquie Malawi Nigéria Nigéria Côte d’Ivoire | 1992 2008 2009 2013 2013 2014 2015 | 19.6% 82.5% 63.9% 47.8% 37.2% 59.9% 77% |