In the period since the mid 1970s, patterns of family formation and reproduction have changed. The trends in North America and Europe show later and less frequent marriages, declining fertility rates, often below replacement levels, and rising divorce rates although the majority of divorcees remarry. The change in family formation and reproduction reflects a number of complex socio-economic factors. Modern family planning methods, the introduction or liberalization of divorce laws, better access for women to higher education, women's need to and interest in pursuing paid work, but also the increasing costs of bringing up and educating children and the geographic mobility of labour could go some way towards explaining this fundamental social transformation.
During the 1980s, the size of the average household, as measured by the number of persons per household, diminished in most EEC/EU countries. The size of the average household in the EEC/EU countries, for example, decreased in all countries, through to a various degree. In 1990 it averaged from 1.7 persons in Denmark to 3.4 persons in Spain.