Blackwell Reference Online

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Childbearing, or the fertility of human populations, has changed profoundly in the last several centuries. Four aspects are basic for measuring and studying human fertility: age , parity (number of children ever born), length of birth interval , and population reproductivity . Additionally, there are cross-cutting issues of time perspective and of fertility dimensions. The variety of fertility measures at a given time is both a result of the data available and a precondition to expansions in data collection efforts. Fertility measures are expressed to reflect childbearing either in the time period in which they occur, or at the end of the (reproductive) life time of a cohort. Period fertility rates and analyses are cross-sectional and give a “snapshot” of a population for a short period of time. A major advantage of period rates is that they are immediately calculable. A second is that they provide the annual contribution to population growth through fertility. Cohort fertility rates and analyses concern a group of persons with a common temporal experience, such as a birth or marriage date. They take into account the events occurring to women (or men) until the end of their reproductive years. More stable than period rates, they provide the means to evaluate long-term population evolution. The main disadvantage in calculating cohort measures is that they require, at minimum, ... log in or subscribe to read full text