1 This release contains estimates of the resident population of Statistical Areas Levels 2 to 4 (SA2s - SA4s) and Greater Capital City Statistical Areas (GCCSAs) of Australia as at 30 June 2001 to 30 June 2018, by age and sex. These estimates plus those for Local Government Areas are provided in the Data downloads section of this issue.
2 To meet the competing demands for accuracy and timeliness, there are several versions of sub-state population estimates. Preliminary estimates by age and sex as at 30 June are normally available by August of the following year, revised estimates 12 months later and rebased and final estimates after the following Census. The estimates in this issue are final for 2001 to 2016, revised for 2017, and preliminary for 2018.
3 The estimates in this issue are consistent with the total sub-state estimates released in the 2017-18 issue of Regional Population Growth, Australia (cat. no. 3218.0) on 27 March 2019 and the state/territory estimates by age and sex released in the September 2018 issue of Australian Demographic Statistics (cat. no. 3101.0). Subsequent updates to state/territory population estimates will be incorporated in future issues of Regional Population by Age and Sex, Australia (cat. no. 3235.0).
Estimated resident population
4 Estimated resident population (ERP) is the official estimate of the Australian population, which links people to a place of usual residence within Australia. Usual residence within Australia refers to that address at which the person has lived or intends to live for six months or more in a given reference year. For the 30 June reference date, this refers to the calendar year around it. More detailed explanations of the concept of ERP, as adopted by the ABS for official population estimates, are contained in Population Estimates: Concepts, Sources and Methods (cat. no. 3228.0.55.001).
5 Estimated resident population is based on Census counts by place of usual residence (excluding short-term overseas visitors in Australia), with an allowance for Census net undercount, to which are added the estimated number of Australian residents temporarily overseas at the time of the Census.
Australia, states and territories
6 Population estimates for Australia and the states and territories (from now on referred to as states) are updated by adding to the estimated population at the beginning of each period the components of natural increase (births minus deaths, on a usual residence basis) and net overseas migration. For state populations, interstate migration is also accounted for.
Statistical Area Level 2 (SA2)
7 In Australia, the SA2 (as defined in the Australian Statistical Geography Standard (ASGS)) is the base spatial unit used to collect and disseminate statistics other than those collected from the Census. In aggregate, SA2s cover the whole of Australia without gaps or overlaps. Populations for SA2s are estimated as at 30 June each year. Population estimates for larger regions are built up from SA2-level estimates.
8 The ERP as at Census date for each SA2 is calculated based on usual residence Census counts, excluding short-term overseas visitors in Australia, with an allowance for Census net undercount and the number of residents temporarily overseas (RTOs) at the Census date. The estimates of net undercount are apportioned to SA2s based on age, sex, Indigenous status, state and territory, and broad region. The number of RTOs on Census night is estimated based on coding addresses of residence to SA2 from a sample of incoming passenger cards provided by the Department of Home Affairs. As the Census is not held on 30 June (the 2016 Census was held on 9 August), further adjustments to account for births, deaths and migration for the intervening period are made to obtain the ERP at 30 June. A procedure is then applied to avoid the release of unconfidentialised usual residence Census counts while maintaining consistency with the unconfidentialised ERP.
9 SA2 populations are updated in post-Census years (from 2016) by adding to the estimated population at the beginning of each period the components of natural increase (births minus deaths), net internal migration (moves between and within the states) and net overseas migration. This method and its data sources are explained in Feature Article: New Methodology Used to Prepare Sub-state Population Estimates. In some very small areas, population change since the previous Census may be assumed to be zero in the absence of reliable component data for these areas. All estimates are scrutinised and validated by ABS analysts. Local knowledge, such as that advised by state governments (including peer reviewers) is considered and used to adjust the figures for particular SA2s. Estimates at the SA2 level are constrained so that they add to the relevant state population estimates.
10 Total population estimates for each SA2 for post-Census years are then broken down by age and sex by ageing the previous year's population by one year, and incorporating the components of population change - births (by sex), and deaths, internal and overseas migration (by age and sex). Further information on these components is contained in the Explanatory Notes of Regional Population Growth, Australia (cat. no. 3218.0). Prior to 2016, the internal and overseas migration components were based on migration profiles from the previous Census. For areas where the components are of insufficient quality, adjustments are made. These components are confidentialised and constrained to add to the relevant state component estimates by age and sex. The resultant ERPs are subsequently constrained to state population estimates by age and sex. As a result of confidentialisation and forced additivity, estimates of under three people should be regarded as synthetic and only exist to ensure additivity to higher levels. While output is presented by five-year age group (up to 80 to 84 years, then 85 years and over), all calculations are made at single year of age level (up to 99 years, then 100 years and over). Population estimates based on single year of age may be available on request as a charged consultancy.
11 While sub-state ERP by age and sex is consistent with state ERP by age and sex, differences arise between aggregated sub-state components by age and otherwise published state components by age. This is due to the different reference period of sub-state ERP (annual as at 30 June) and state ERP (quarterly), as the age of a person at the end of the financial year can be different to the age of that person at the end of each quarter.
12 In Census years, both preliminary estimates (derived from updating ERP from the previous Census) and rebased population estimates (based on the current Census) are prepared. Differences between these two sets of estimates are referred to as intercensal differences. Rebased estimates of SA2 populations for previous intercensal years are derived by apportioning the intercensal difference across the five years, while constraining to state estimates. Rebased 2012 to 2015 estimates were generally derived by adding one-fifth of the 2016 intercensal difference to the previous estimate of the 2012 population, two-fifths to the previous estimate of the 2013 population, and so on.
Statistical Area Level 1 (SA1) and SA1-based geographies
13 The SA1 is the smallest geographic unit for the release of Census data. There are approximately 57,500 SA1s and they cover the whole of Australia without gaps or overlaps. To provide some indication of ERP below the SA2 level, the ABS prepares population estimates for SA1s, which are then aggregated to regions such as Remoteness Areas and electoral divisions. By this means, population estimates for areas other than those provided in this product (including SA1s) may be available on request as a charged consultancy.
14 Population estimates at the SA1 level as at 30 June of a Census year are compiled by apportioning the estimate for each SA2 across the SA1s within the SA2, using Census usual residence counts by age and sex. In intercensal years, total population estimates for SA2s are apportioned across SA1s by taking into account population change implied by Medicare enrolments and Australian Electoral Roll counts at the SA1 level in the years following the Census. These total SA1 populations are then broken down by age and sex by ageing the previous year's population, with age distributions for selected areas held static.
Local Government Area (LGA)
15 In Census years, LGA ERP by age and sex is aggregated from whole SA2 or SA1 level estimates by age and sex where possible. Where LGAs cross SA1 boundaries, Mesh Block Census counts are used to estimate the share of the SA1 population that reside in those LGAs. LGA population estimates are updated in intercensal years from 2016 by accounting for the components of population change. The resulting LGA ERP by age and sex is constrained to SA2 ERP by age and sex to ensure consistency between these two geographies, based on the smallest possible regions where SA2 and LGA boundaries match in terms of the combined area containing resident population. For example, where one LGA aligns exactly with one SA2 or where a group of LGAs aligns with a group of SA2s, the ERP for these areas will generally match.
16 To enable the comparison of regional populations over time, historical population estimates based on consistent updated geographic boundaries are prepared, for example when boundaries of Local Government Areas change. These estimates correspond with previously released estimates (on different boundaries) where possible.
Accuracy of sub-state population estimates
17 In recognition of the inherent difficulty involved in estimating population, population figures in text and accompanying summary tables published by the ABS are generally rounded. In the commentary for this product, figures less than 1,000 are rounded to the nearest ten, figures over 1,000 are rounded to the nearest hundred, and figures over 1 million are rounded to the nearest 10,000 or 100,000. While unrounded figures are provided in the spreadsheets, accuracy to the last digit should not be assumed. Percentages and estimates of change in population are based on unrounded numbers.
18 Areas with a total population of less than 1,000 people at 30 June 2018 have been excluded from commentary in this issue.
Australian statistical areas
19 This publication contains data presented according to the 2016 edition of the Australian Statistical Geography Standard (ASGS), which refers to boundaries as defined at 1 July 2016. Under this classification, statistical areas are defined as follows:
- Statistical Areas Level 2 (SA2s). SA2s are medium-sized general purpose areas which aim to represent communities that interact together socially and economically. SA2s are based on officially gazetted suburbs and localities. In urban areas SA2s largely conform to one or more whole suburbs, while in rural areas they generally define the functional zone of a regional centre.
- Statistical Areas Level 3 (SA3s). SA3s are aggregations of whole SA2s and reflect a combination of widely recognised informal regions as well as administrative regions such as state government regions in rural areas and Local Government Areas in urban areas.
- Statistical Areas Level 4 (SA4s). SA4s are made up of whole SA3s and are designed to reflect labour markets. In rural areas, SA4s generally represent aggregations of small labour markets with socioeconomic connections or similar industry characteristics. Large regional city labour markets are generally defined by a single SA4. Within major metropolitan labour markets SA4s represent sub-labour markets.
- Greater Capital City Statistical Areas (GCCSAs). GCCSAs are built from whole SA4s and represent a broad socioeconomic definition of each of the eight state and territory capital cities. They contain not only the urban area of the city, but also the surrounding and non-urban areas where much of the population has strong links to the capital city, through for example, commuting to work.
20 This product also contains data presented according to the 2018 edition of the Australian Statistical Geography Standard (ASGS) - Non ABS Structures.
- Local Government Areas (LGAs). LGAs are ABS approximations of officially gazetted LGAs as defined by each state and territory local government department. LGAs cover incorporated areas of Australia, which are legally designated areas for which incorporated local governing bodies have responsibility. The ABS updates LGAs annually, and prepares updated and historical population estimates based on these updated boundaries.
21 Further information on these statistical areas is contained in:
Australian Statistical Geography Standard: Volume 1 - Main Structure and Greater Capital City Statistical Areas, July 2016 (cat. no. 1270.0.55.001)
Australian Statistical Geography Standard: Volume 3 - Non ABS Structures, July 2018 (cat. no. 1270.0.55.003)
22 Maps for Australian statistical areas are available in the online mapping tool ABS Maps. A complete series of SA2 maps is available to download from Australian Statistical Geography Standard: Volume 1 - Main Structure and Greater Capital City Statistical Areas, July 2016 (cat. no. 1270.0.55.001).
Population pyramid graphs
23 Population pyramids are used in this issue to illustrate the age and sex distribution of a population. In each case, five-year age groups are represented on the vertical axis of the graph. For pyramids showing percentage distribution in this product, the population in each age-sex group in an area is expressed as a percentage of the total population in that area. Thus, the sum of the percentages indicated by the bars of one colour in a population pyramid will be 100% of the population of the area represented by that colour, e.g. Greater Sydney. Further, the sum of the percentages indicated by the bars of the other colour will be 100% of the population of the area represented by the other colour, e.g. the rest of NSW. By using this method, the age and sex distribution of two areas can be compared irrespective of the relative sizes of the total populations of the areas.
24 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.
25 Other ABS releases that are freely available on the ABS website and may be of interest to users of this product include:
Australian Demographic Statistics (cat. no. 3101.0)
Regional Population Growth, Australia (cat. no. 3218.0)
Births, Australia (cat. no. 3301.0)
Deaths, Australia (cat. no. 3302.0)
Migration, Australia (cat. no. 3412.0)
Australian Historical Population Statistics (cat. no. 3105.0.65.001)
Population Projections, Australia (cat. no. 3222.0)
Information Paper: Population Concepts (cat. no. 3107.0.55.006)
Population Estimates: Concepts, Sources and Methods (cat. no. 3228.0.55.001)
Quality Assurance of Rebased Population Estimates, 2016 (cat. no. 3250.0.55.001)
Additional statistics available