Visualising the demographic factors which shape population age structure

Tom Wilson

doi:10.4054/DemRes.2016.35.29

Volume 35 - Article 29 | Pages 867–890

Visualising the demographic factors which shape population age structure

By Tom Wilson

Date received:

6 Jun 2016

Date published:

22 Sep 2016

Word count:

4237

Keywords:

age structure, components of change, data visualization, migration, population pyramids

DOI:

10.4054/DemRes.2016.35.29

Replicable Material:

demographic-research.35-29 (zip file, 367 kB)
readme.35-29 (text file, 327 Byte)

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Abstract

Background: The population pyramid is one of the most popular tools for visualising population age structure. However, it is difficult to discern from the diagram the relative effects of different demographic components on the size of age-specific populations, making it hard to understand exactly how a population’s age structure is formed.

Objective: The aim of this paper is to introduce a type of population pyramid which shows how births, deaths, and migration have shaped a population’s age structure.

Methods: Births, deaths, and population data were obtained from the Human Mortality Database and the Australian Bureau of Statistics. A variation on the conventional population pyramid, termed here a components-of-change pyramid, was created. Based on cohort population accounts, it illustrates how births, deaths, and net migration have created the population of each age group. A simple measure which summarises the impact of net migration on age structure is also suggested.

Results: Example components-of-change pyramids for several countries and subnational regions are presented, which illustrate how births, deaths, and net migration have fashioned current population age structures. The influence of migration is shown to vary greatly between populations.

Conclusions: The new type of pyramid aids interpretation of a population’s age structure and helps to understand its demographic history over the last century.