Official records state that 28.7 of the population of people in Nigeria still practice open defecation.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/nigeria-over-28-residents-nigeria-still-practice-open-defecation-govt
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/all-africa
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sanitation
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/open-defecation
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nigeria
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/toilets
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/africa