Bringing mortality back into our understanding of fertility change: revisiting the onset of fertility transitions using net reproduction measures

This paper argues for the reintegration of mortality into studies of fertility transition by using net reproduction measures rather than solely focusing on total fertility rates (TFR). Accounting for mortality through metrics like the 2-Sex Net Reproductive Rate (2SNRR) would change our understanding of fertility transitions globally. Using global data for 236 countries (1950–2023), the analysis shows that the 2SNRR-based fertility transitions typically occur later, at lower peak levels, and with less dramatic declines than TFR-based assessments suggest. This difference is particularly pronounced in regions with high mortality rates, such as parts of Africa and Southern Asia. The study reveals that seven countries have yet to begin their fertility transitions when mortality is considered, challenging the notion that fertility decline is universal. Incorporating mortality into fertility analyses provides a more nuanced understanding of demographic transitions and has important implications for population policies and the degree to which current and historical reproductive patterns differ from net replacement levels.