Volume 44 - Article 2 | Pages 49–66

Born once, die once: Life table relationships for fertility

By Annette Baudisch, Jesús-Adrián Alvarez

Print this page  Facebook  Twitter


Date received:18 May 2020
Date published:06 Jan 2021
Word count:4032
Keywords:birth expectancy, birth table, fertility, mean age at first birth, standard deviation


Background: Everyone dies, and only once. This basic truth underlies all formal mortality research. Similarly, everyone is born, and only once. This basic truth has not been fully exploited to benefit formal fertility research. An advance has recently been made by Baudisch and Stott (2019), who conceive a population of unborn children awaiting the event of their own birth. This approach introduces a novel survivorship concept for birth.

Results: Formalizing the idea of “birth survival,” here we define the underlying random variable and derive the central triplet of survival analysis functions – hazard, density, and survival. We demonstrate that using a “born once, die once” analogy results in a straightforward framework to capture age-specific patterns of birth, analogous to classical life table functions. Based on a single variable (age-specific birth counts), we construct a “birth table” and, from there, meaningful summary measures such as “birth expectancy” and associated measures of spread.

Contribution: We advance a new framework to enrich the toolbox of fertility research. The relationships developed here serve to compare birth schedules across populations and reveal macro- level patterns and constraints. The triplet of birth functions and the birth table set the stage to transfer methods from mortality to fertility research. They offer a starting point to study birth and death within the same framework and for the same focal individual. With analogous formal methods, studies of the intertwined relationships between birth and death become possible. This, we envision, will open an entirely unexplored line of research.

Author's Affiliation

Annette Baudisch - Syddansk Universitet, Denmark [Email]
Jesús-Adrián Alvarez - Syddansk Universitet, Denmark [Email]

Other articles by the same author/authors in Demographic Research

» The threshold age of the lifetable entropy
Volume 41 - Article 4

» Evolution of fixed demographic heterogeneity from a game of stable coexistence
Volume 38 - Article 8

» The pace of aging: Intrinsic time scales in demography
Volume 30 - Article 57

» How life expectancy varies with perturbations in age-specific mortality
Volume 27 - Article 13

» Senescence vs. sustenance: Evolutionary-demographic models of aging
Volume 23 - Article 23

Most recent similar articles in Demographic Research

» How much time is left? International trends in parenthood expectancy
Volume 48 - Article 16    | Keywords: mean age at first birth

» Union formation and fertility amongst immigrants from Pakistan and their descendants in the United Kingdom: A multichannel sequence analysis
Volume 48 - Article 10    | Keywords: fertility

» The sex preference for children in Europe: Children’s sex and the probability and timing of births
Volume 48 - Article 8    | Keywords: fertility

» Parental status homogeneity in social networks: The role of homophilous tie selection in Germany
Volume 48 - Article 2    | Keywords: fertility

» Investigating the application of generalized additive models to discrete-time event history analysis for birth events
Volume 47 - Article 22    | Keywords: fertility