Sources of Error and Bias in Methods of Fertility Estimation Contingent on the P/F Ratio in a Time of Declining Fertility and Rising Mortality

Tom A. Moultrie, University of Cape Town

The most commonly used indirect fertility estimation methods rely on the use of the P/F ratio, first proposed by Brass. In essence, the ratio compares cumulated cohort fertility with cumulated period fertility on the basis of three, fairly strong, assumptions. First, that fertility rates have been constant over time. Second, that the age distribution of fertility has been constant; and third, that the fertility of women who do not survive to report their numbers of children borne does not differ from those who do survive. The intention of this paper is to interrogate what happens to the results produced by the P/F ratio method as each of these three assumptions is violated, first independently, and then concurrently. These investigations are important given the generally poor quality of census data collected in developing countries, particularly sub-Saharan Africa, and the particular demographic dynamics associated with a generalised HIV/AIDS epidemic in the region.