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%