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UNDERSTANDING THE 'HOWS AND WHYS' OF REGIONAL POPULATION GROWTH: WHAT'S DRIVING CHANGE IN OUR REGIONS
Sub-state population estimates have traditionally been prepared using a regression-based approach, where population change was estimated based on changes in indicator data sources (e.g. dwelling approvals, and Medicare and Australian Electoral Commission enrolments). To date, regression modelling has provided reasonable accuracy, however it is inconsistent with the method used to prepare national, state and territory population estimates, and it does not provide an understanding of how and why population changes in a region.
The ABS has a long-established time series of births and deaths data at the sub-state level, and has invested significant effort in recent years to develop an effective and timely method of estimating regional internal migration. This has allowed a model to estimate the remaining component - regional overseas migration - to be developed. As such, the ABS has now implemented the component method to prepare sub-state population estimates. This provides a much richer picture of regional population change, particularly the factors that drive such change, that previously has not been possible.
This article is the first in a series that will examine the components of population change and their contribution to population growth at the regional level.
COMPONENTS OF POPULATION CHANGE: A CAPITAL CITY COMPARISON, 2016-17
Population change at the sub-state level can be considered in terms of three main components: natural increase, net overseas migration and net internal migration. Although the number of people in all capital cities grew in the year ended 30 June 2017, the proportion that each of these components contributed to population change varied substantially between the cities (see Figure 1).
Figure 1. COMPONENTS OF POPULATION CHANGE, Greater Capital Cities, Australia, 2016-17
Melbourne experienced the largest population growth of all capital cities in 2016-17, increasing by 125,400 people, with each component contributing to this growth. Net overseas migration was the major contributor, accounting for 64% (80,000 people) of the total population change in Melbourne. Natural increase made up 29% (36,300), while net internal migration accounted for 7.3% (9,200) of population growth.
Sydney's population increased by 101,600 in 2016-17 and, as was the case for Melbourne, net overseas migration was the major contributor (84,700 people) to this growth. However, unlike Melbourne, Sydney experienced a net internal migration loss in 2016-17, meaning 18,100 more people left the city to move to other parts of Australia than arrived in Sydney from other parts of the country. Sydney lost most people to other parts of New South Wales (40,000 people) and Melbourne (14,400).
In Brisbane and Hobart, the relative contribution of each component was more even. In Brisbane, net overseas migration and natural increase each accounted for around 37% of population growth in 2016-17 (18,000 people each), whilst net internal migration made up the remaining 25% (12,000 people). In Hobart, net internal migration contributed 36% of population growth (880 people), net overseas migration 35% (840) and natural increase 29% (700).
Natural increase was the major contributor to population change in Perth and the Australian Capital Territory (ACT). In Perth, natural increase accounted for 16,300 of the 21,100 population increase in 2016-17. Net overseas migration contributed 11,700 people, whilst there was a net internal migration loss of 6,900 people. In the ACT, natural increase contributed to 49% of population change in 2016-17 (3,400 people), net overseas migration 41% (2,800) and net internal migration 9.7% (660).
In Adelaide, population gains from natural increase (5,500) were negated by net internal migration losses (-5,500), leaving a net overseas migration (and total population) gain of 9,600 people. A similar pattern was observed in Darwin, where a natural increase of 1,900 people was offset by a net internal migration loss of 1,900 people, leaving a small net overseas migration (and total population) gain of 700 people.
COMPONENTS OF POPULATION CHANGE: AUSTRALIA'S LARGEST-GROWING SA2s, 2016-17
Just as the relative contributions of the components of population change vary between capital cities, they can also vary within cities and regions. Understanding the drivers behind population change is crucial because the different components that contribute to change may require different planning strategies and policy responses.
Figure 2 presents population component data for the largest growing Statistical Areas Level 2 (SA2) in Australia in 2016-17.
Figure 2. COMPONENTS OF POPULATION CHANGE, Top 10 largest-growing SA2s, Australia, 2016-17
The SA2 with the largest growth in Australia was Cranbourne East, in Melbourne's outer south-east, increasing by 7,300 people in 2016-17. Net internal migration accounted for 85% (6,300 people) of this growth. More people moved into Cranbourne East from other parts of Australia (8,000) than any other SA2 in the country in 2016-17.
Like Cranbourne East, Cobbitty - Leppington, in Sydney's outer south-west, is an area on the metropolitan fringe which has experienced large population growth in recent years due mainly to positive net internal migration. Around 3,700 more people moved into this SA2 than moved out in 2016-17, accounting for 90% of its population growth.
Similar patterns were observed in the outer-suburban SA2s of Riverstone - Marsden Park in Sydney's north-west, Mernda in Melbourne's north-east, Ellenbrook in Perth's north-east, and Pimpama, an outer northern suburb of the Gold Coast.
For other areas, such as the neighbouring SA2s of Tarneit and Truganina in Melbourne's outer west, the contribution of all three components was more even. In Tarneit, 45% of population change in 2016-17 could be attributed to positive net internal migration, compared with 29% to net overseas migration and 27% to natural increase. Tarneit had the highest number of births (930) for all SA2s in Australia in 2016-17. In Truganina, 49% of population change in 2016-17 could be attributed to positive net internal migration, compared with 26% to net overseas migration and 25% to natural increase.
In contrast to the outer-metropolitan suburbs discussed above, population growth in the inner-city areas of Australia's capital cities has been mainly driven by overseas migration. The SA2 of Melbourne experienced a population increase of 4,600 people in 2016-17. Net overseas migration contributed 3,600 people to this total, representing 77% of Melbourne's population change. Melbourne attracted more overseas migrants than any other SA2 in Australia (10,600) in 2016-17, but also lost the most through outgoing migration (7,000).
Waterloo - Beaconsfield, an inner-city SA2 in Sydney's south, grew by 2,600 people in 2016-17. Net overseas migration contributed to 68% of this change (1,800 people), compared with 18% (470) from net internal migration and 14% (370) from natural increase.
Whilst this article has focussed on Australia's capital cities and ten largest-growing SA2s in 2016-17, the contributions of the three drivers of regional population change can now be assessed for any area in the country, due to the adoption of the component method to calculate sub-state population estimates. Even in areas where there have been relatively small changes in population overall, there can be substantial variations in one or more of the population components; variations that may have previously gone unnoticed. Moving beyond just describing how much regional populations have changed, to understanding why these changes have occurred is now not only possible, but imperative for better population planning.
For more information about the component method, see the Feature Article, 'New Methodology Used to Prepare Sub-state Population Estimates', which can be accessed via the left navigation panel of this publication.
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