Measuring the Prevalence of Multipartner Fertility Independent of Fertility Level

Abstract

The prevalence of multipartner fertility (W) depends on both the level of fertility (TFR) and the likelihood (s) that a woman has a birth of parity 2 or higher by a different partner. The relationship between those factors is analyzed, and the joint variability of W with TFR and s is shown for a range of contemporary values. Similar calculations are made for the fraction of children with a maternal half sibling. Index S is then proposed as a measure that can approximate the probability that a woman has a birth by a different partner based on the TFR and the observed prevalence of multipartner fertility or children with half siblings.