Page 93 - IJPS-10-4

International Journal of

Population Studies

RESEARCH ARTICLE
Long-term impact of mortality on population

age structures

Gustavo De Santis * and Giambattista Salinari 2
1
1 Department of Statistics, Computer Science, Applications (DiSIA), University of Florence, Italy
2 Department of Economics and Business, University of Sassari, Italy

Abstract

In this study, we tested the hypothesis that mortality has a greater influence than
fertility on shaping population age structures in the long run and that recent mortality
rates provide a satisfactory initial approximation for describing observed age
structures in most empirical cases. In the theoretical part of this article, we elucidate
a potential fallacy in the line of reasoning based on simulations and counterfactuals
frequently used to attribute population aging to low fertility rates. The alternative
view that we propose leads us to hypothesize that age structures conform, albeit
not exclusively, to a standard derived from survival conditions: the age structure of a
stationary population within a given period. We tested this hypothesis on all countries,
using the data from the United Nations database (1951 – 2021) and specifically on 10
European countries using the data from the Human Mortality Database (1860 – 2019).
The empirical results indicate that current survival conditions sufficiently explain a
significant portion of the observed age structure across all examined countries and
epochs. However, deviations from this underlying, long-term (mortality-driven) path
exist, which our approach cannot fully explain. This is where the role of fertility arguably
*Corresponding author: becomes more prominent. Several implications arise from our findings, including the
Gustavo De Santis
(gustavo.desantis@unifi.it) debate on the relative role of fertility and mortality in shaping age structures in the
long run, the theoretical meaning and practical use of cross-sectional life tables, and
Citation: De Santis, G. &
Salinari, G. (2024). Long-term the notion and measure of demographic dividends.
impact of mortality on population
age structures. International Journal
of Population Studies, 10(4): 87-97. Keywords: Age structure; Aging; Stationary population; Mortality; Fertility; Index of
https://doi.org/10.36922/ijps.377 dissimilarity
Received: September 29, 2023
Accepted: January 2, 2024
Published Online: March 19, 2024 1. Introduction
Copyright: © 2024 Author(s). This article focuses on the determinants of population age structures and their evolution,
This is an Open-Access article
distributed under the terms of the with special regard to population aging. In this field, there is a significant divide between
Creative Commons Attribution expert opinions, as shown in the excerpt below:
License, permitting distribution, “Why are populations of rich countries so much older today than they were a century
and reproduction in any medium,
provided the original work is or two ago?... Is the main driver falling mortality and lengthening life, or is it falling
properly cited. birth rates and slowing population growth? Common sense suggests that longer life
Publisher’s Note: AccScience is responsible for population aging, but decades ago, the work of demographers such
Publishing remains neutral with as Coale (1956; 1957) and Keyfitz (1975) persuaded us that, in fact, fertility decline
regard to jurisdictional claims in
published maps and institutional was more important. More recently, a new wave of demographic analysis suggests
affiliations. that mortality decline is the main demographic source of continuing population

Volume 10 Issue 4 (2024) 87 https://doi.org/10.36922/ijps.377