Emmanuel Todd has gathered some interesting data on polygamy (actually polygyny) rates.
The world champion is Burkina Faso! Over half of its married women have co-wives. (What do all the leftover men do?)
Arab and African Polygamy Rates
(% of married women with co-wife)
|Ivory Coast Catholics||24.7|
|Ivory Coast Muslims||44.5|
|Ivory Coast Animists||47.2|
In Arab countries 5-10% of women are in polygamous marriages. In black Africa, 30-55% of women. The highest levels are in interior West Africa.
Another difference: Arab-style marriage of parallel cousins [father’s brother’s daughter] is uncommon in Africa. Instead cross-cousin [between the children of brother and sister] or exogamous marriage is the norm.
Youssef Courbage and Emmanuel Todd, A Convergence of Civilizations: The Transformation of Muslim Societies (Columbia UP, 2011) p. 44.