Some Demographic Consequences of Changing Cohort Fertility Patterns: An Investigation Using the Gompertz Function.

The purpose of this article is to formulate some convenient summary measures for describing female lifetime fertility experience and, using these measures, to investigate certain macro-demographic consequences of changes in cohort childbearing patterns. Authors' aim is in part to report some substantive results relating to the effects of fertility changes and in part to illustrate what they think is a promising methodological approach. This article formulates some convenient summary measures of fertility patterns. These measures, which are based on the Gompertz function, are total lifetime fertility, median age of mothers at childbirth, and inter-quartile range of age of mothers at childbirth. Estimates of the parameters of Gompertz function, based on Canadian data, are used to derive, for each of the summary measures, values, which reflect historical fertility experience, and thus give an impression about the range of realistic values for these measures. A simple model of demographic activity, which includes the Gompertz function, is also considered, and this model is used in computer simulation experiments to determine the macro-demographic effects of changes in each of the three summary measures.