Polygyny is the system under which a man is married to two or more wives at the same time; it includes bigamy which is the (usually illicit) marriage to two women; and where polygamy is forbidden under the law, it can take the form of cohabitation with many women. As well as being discriminatory against women, men who cannot afford the bride-price and therefore cannot wed, can also be perceived as victims of this nuptial practice. Although polygyny ensures the birth of many children, as well as an additional supply of labour (both of which contribute, in traditional societies, to the wealth and prestige of the family), in a changing society it causes a strain on economic resources and can be a barrier to population control.
Polygamy in its traditional form occurs mainly in Africa, although concubinage still exists in Asia. Harems exist in Arabia and the Middle East but the Muslim law of taking up to four legal wives is much less followed in current practice, particularly because of the cost. It has been abolished in certain countries (Tunisia, Turkey), and severely restricted elsewhere (Pakistan, Egypt). But the rich in both Asia and Arabia continue to keep harems and this encourages traffic in women and children, particularly to Arabia. Bigamy occurs in isolated cases throughout developed society. A feature of the Mormon religion used to be polygamy, but the practice was outlawed in 1896 as a condition for Utah to become a state in the USA.