Cohabitation is the living together of a couple as in marriage, but without the legal or religions sanction of marriage and the resulting constraints. The children of cohabiting couples are illegitimate, and as such they may not be entitled to social benefits or inheritance of property. Cohabitation has become increasingly popular in sophisticated society, where it may be caused by a lack of religious conviction, a search for new forms of life-style and rejection of traditional values, unequal taxation, or the inability of one or both parties to obtain a divorce or dissolution of a previous marriage; a state of cohabitation may be imposed on an otherwise married couple because of the non-validity of their marriage or the non-validity of previous divorce. Cohabitation with a number of women may be the result of a reversion to the custom of polygamy which is prohibited under the law.
Legal marriage is increasingly being preceded or replaced by cohabitation or other forms of consensual union. Such union often starts at ages below those of entry into legal marriage. In North America, Europe and the USSR, at least in urban areas, the practice of cohabitation or sexual intimacy outside marriage has become an accepted norm in less than two decades. Cohabitation is still most often a precursor to marriage, although an increasing number of couples are choosing never to marry. Cohabitation or consensual unions are also extremely frequent in other less industrialized societies, particularly in Latin America. Census data show celibacy rates at various ages in a number of Latin American countries which clearly reflect a high incidence of consensual unions. This is not a new form of behaviour among the poorer social groups, but it is spreading along the ladder of the social classes, from the bottom, and also to some extent from the top, to the middle class.
In the UK a study in 1993 correlated a 10-fold increase in reported crime between 1955 and 1991 with growth of cohabitation, divorce and births outside marriage. The proportion of women in the UK who had cohabited with their future husbands prior to marriage rose from approximately 5% in the mid-1960s to over 50% in 1991. It is expected to rise to 80% by 2000. In 1993, 30% of children were born outside marriage, with about half of these to cohabiting parents.
Cohabitation as a way of life is practised by certain racial groups; in the West Indies, though not so much among Latin Americans, it is customary for couples to change partners, resulting in the children of such unions being deprived of a stable family environment and suffering from loss of identity. In an extended family situation, such children may be cared for by relatives; but where the practice is continued after immigration to an industrialized country, the children are often abandoned.