Age, Period, and Cohort Effects in Demography
Demographic events such as birth, death, marriage, and migration are all influenced by age, period, and cohort in one way or another. For example, identification of patterns in mortality, nuptiality, and fertility by Coale and his associates is based on age (Coale and Demeny, 1983; Coale, 1971b; Coale and Trussell, 1974). Hence, age is an extremely important variable in most social and behavioral science research. Although the models based on age have been very important and useful in the development of modern demographic research, these models are still inadequate. Ignoring period and cohort effects in the interpretation of demographic processes results in error. In the study of fertility, Page (1977) developed a model which takes into account both age and duration. This model not only fits the data better than the one based solely on age, but also penetrates deeper into the structure of underlying fertility schedules and hence it is more revealing. Page argues as follows: “Age cannot bear the same relation to fertility experience in all populations, because the age at which women begin childbearing can vary widely. For populations in which childbearing occurs predominantly within marriage, duration of marriage is a more direct specification than age for detecting patterns of control” (pp. 86–87). She stresses the fact that duration alone is not sufficient as age also determines childbearing.
KeywordsLabor Force Labor Force Participation Divorce Rate Labor Force Participation Rate Marriage Cohort
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