Marriage emerged as the most popular institution throughout history primarily because it was an effective arrangement to improve the care and upbringing of children. Marriage is not necessary to have children, but it has been of enormous importance in the rearing of children. Birds and other non-human species do not have “marriage”, but both parents are often involved in raising their offspring.
With the sharp declines in birth rates since 1970 in Western and other rich countries, including much larger fractions of adults who do not have any children, both men and women have significantly increased their ages at marriage, and sharply raised their propensities to divorce. In 1950, a typical woman and man married at ages 20.3 and 22.8, respectively, whereas now the typical marital ages are 26.0 and 27.7, respectively. These changes in age at marriage are related to reduced demand for many children, increased college education of both men and women but especially of women, much greater labor force participation of married and divorced women, and the narrowing of the gender gap in earnings.