life-cycle A widely used metaphor denoting the passage of an individual through the successive stages of life, from birth to death through childhood, adolescence, adult life, and old age, and implying a return to infancy in old age. The term is broadly synonymous with those of life-course and life-stages.

In some societies, these stages are collectively defined by membership of an age-grade or age-set. In Western societies, certain transition points, such as the age of consent to sexual intercourse, the age of legal majority, or the age when education ceases to be compulsory, are defined and regulated by law, but the stages of the life-cycle are otherwise loosely structured and allow a degree of personal choice, for example in the age of marriage. For this reason, research analyses rarely use age alone to define stages in the life-cycle, the more common approach being to use marital status and the presence of children in full-time education, or under school-leaving age, who live with the respondent. Among men, the category of prime-age males is often separately identified, especially in labour-market analyses: these are men in the prime of life, usually defined as aged 25 to 55 years (sometimes 25 to 50 years), when employment levels are at their highest. Demographic analysts identify fewer life-cycle groups than would sociologists: for them the two dependent groups are children under 15 years and old people aged 65 (or 60) and over, who are supported financially and otherwise by the population of working age or active population.

Life-cycle stage is a variable often used in analyses of employment patterns, housing preferences and needs, patterns of social relationships in the community and the extended family, studies of poverty, and migration patterns. However, although still widely employed, it has dropped out of favour in modern socio-demographic literature because of its normative resonances. See also LIFE-EVENT.