November 11, 2025 | News | Overview

Recommended Reading

Here is an overview of the latest reading recommendations for papers published by scientists at the MPIDR.

Rethinking Formal Demography: Birth as an Event Experienced by the Child

Paper published October 3, 2025

In a recent methodological paper, Annette Baudisch (University of Southern Denmark) and Antonino Polizzi (Max Planck Institute for Demographic Research) use methods from mortality research to describe when children are born in the parental life course.

The authors build on the “Born once, die once” approach (B1D1), which views birth as an event experienced by the child, not the parent. From the child’s perspective, birth is a certain event that occurs only once, just like death. The B1D1 perspective uses birth counts by parental cohort and age to calculate density, survival, and hazard functions that describe reproductive timing at the population level. In their new article, Annette Baudisch and Antonino Polizzi reformulate the B1D1 approach, so that density, survival, and hazard functions can be calculated using fertility rates as input. This is important because fertility rates are more frequently used in the study of reproductive timing (“conventional approach”).

The new density, survival, and hazard functions for the conventional approach summarize fertility age patterns without requiring data on individual birth histories or parity. All that is needed are age-specific fertility rates from sources such as the Human Fertility Database or the UN World Population Prospects. “We hope that the functions could be useful to advance conventional fertility research, for example by studying age patterns of fertility in different population groups. Potentially, the functions could also be helpful to improve fertility forecasts,” Antonino Polizzi says.

Original Publication

Annette Baudisch, Antonino Polizzi: Fertility, birth, reproduction: Connecting formal demographic frameworks in Population Studies; DOI: 10.1080/00324728.2025.2550770

Keywords

childbirth, total fertility rate, mean age at birth, quantum, tempo, formal demography, survival analysis, event history analysis, hazard