Regional Population by Age and Sex, Australia methodology

Under a '12/16 month rule', incoming overseas travellers (who are not currently counted in the population) must be resident in Australia for a total period of 12 months or more, during the 16 month follow-up period to then be added to the estimated resident population. Similarly, those travellers departing Australia (who are currently counted in the population) must be absent from Australia for a total of 12 months or more during the 16 month follow-up period to then be subtracted from the estimated resident population.

The 12/16 month rule does not have to be continuous and takes account of those persons who may have left Australia briefly and returned, while still being resident for 12 months out of 16. Similarly, it takes account of Australians who live most of the time overseas but periodically return to Australia for short periods.

The ASGS brings all the regions for which the ABS publishes statistics within the one framework and has been in use for the collection and dissemination of geographically classified statistics since 1 July 2011. It is the current framework for understanding and interpreting the geographical context of statistics published by the ABS.

The delivery of a child, irrespective of the duration of pregnancy, who, after being born, breathes or shows any other evidence of life such as heartbeat.

Refers to the Greater Capital City Statistical Areas of states and territories as defined in the Australian Statistical Geography Standard.

The complete enumeration of a population at a point in time with respect to well-defined characteristics (e.g. Persons, Manufacturing, etc.). When the word is capitalised, "Census" refers to the national Census of Population and Housing.

Death is the permanent disappearance of all evidence of life after birth has taken place. The definition excludes deaths prior to live birth. For the purposes of death registration collections compiled by the ABS, a death refers to any death which occurs in, or en route to Australia and is registered with a state or territory Registry of Births, Deaths and Marriages.

The official measure of the population of Australia, based on the concept of usual residence. It refers to all people, regardless of nationality, citizenship or legal status, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. It includes usual residents who are overseas for less than 12 months over a 16-month period. It excludes overseas visitors who are in Australia for less than 12 months over a 16-month period. Sub-state estimates of the resident population are prepared on an annual basis by adding natural increase (the excess of births over deaths), net internal migration and net overseas migration occurring during the period to the population at the beginning of each period.

Represent the socioeconomic area of each of the eight state and territory capital cities. These boundaries are built from aggregations of whole Statistical Areas Level 4. GCCSA boundaries represent a broad socioeconomic definition of each capital city, containing not only the urban area of the capital city, but also surrounding and non-urban areas where much of the population has strong links to the capital city, through for example, commuting to work.

The difference between two estimates of a Census year population as at 30 June: the first based on the latest Census and the second produced by updating from the previous Census-based estimates which do not take account of information available from the latest Census.

The movement of people across a specified boundary within Australia involving a change in place of usual residence.

The movement of people over a state or territory boundary involving a change in place of usual residence. Net interstate migration (NIM) is the difference between arrivals and departures and can be either positive or negative.

An ABS approximation of an officially gazetted LGA 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 major areas of Australia not administered by incorporated bodies are the northern parts of South Australia and all of the Australian Capital Territory and the Other Territories. These regions are identified as 'Unincorporated' in the LGA structure of the Australian Statistical Geography Standard.

For any distribution, the median value is that which divides the relevant population into two equal parts, half falling below the value, and half exceeding it. Thus, the median age is the age at which half the population is older and half is younger.

The smallest geographic region in the Australian Statistical Geography Standard (ASGS) which forms the basis for all larger regions of the ASGS. They broadly identify land use such as residential, commercial, agricultural and parks. There are approximately 358,000 Mesh Blocks and they cover the whole of Australia without gaps or overlaps.

Excess of births over deaths.

Net overseas migration is the net gain or loss of population through immigration to Australia and emigration from Australia. Under the current method for estimating final net overseas migration this term is based on a traveller's actual duration of stay or absence using the '12/16 month rule'. Preliminary NOM estimates are modelled on patterns of traveller behaviours observed in final NOM estimates for the same period one year earlier.

The difference between the actual Census count (including imputations) and an estimate of the number of people who should have been counted in the Census. This estimate is based on the Post Enumeration Survey (PES) conducted after each Census. For a category of person (e.g. based on age, sex and state of usual residence), net undercount is the result of Census undercount, overcount, differences in classification between the PES and Census, and imputation error.

Overseas migrant arrivals are all overseas arrivals that contribute to NOM. It is the number of incoming international travellers who stay in Australia for 12 months or more over a 16 month period, who are not currently counted within the population, and are then added to the population.

Overseas migrant departures are all overseas departures that contribute to NOM. It is the number of outgoing international travellers (Australian residents and long term visitors to Australia) who leave Australia for 12 months or more over a 16 month period, who are currently counted within the population, and are then subtracted from the population.

The Census Post Enumeration Survey (PES) is a household survey conducted following the Census. The PES allows the ABS to estimate the number of people missed in the Census and the number counted more than once or in error. Historically more people are missed than are counted more than once in Australia, leading to a net undercount. Results from the PES contribute to a more accurate calculation of the estimated resident population on Census night, which is then backdated to 30 June of the Census year.

The 2016 Census of Population and Housing forms the base for newly compiled estimates for 30 June of the Census year, which can be compared with the alternative estimates produced by updating the 2011 Census-based estimates. Of these two estimates, the more recent Census-based estimate is assumed to be the true estimate. To overcome the break in continuity that this implies, population estimates for all years in between the two most recent Censuses are then revised. This complete exercise is known as 'rebasing', as the population estimates are compiled from a new base, the most recent Census.

Estimates of internal migration for Australia's sub-state areas, prepared primarily using Medicare change of address information.

Estimates of overseas migration for Australia's sub-state areas, prepared by breaking down state/territory overseas migrant arrivals and departures primarily using Census information.

Within each state and territory, the area not defined as being part of the Greater Capital City Statistical Area is represented by a Rest of state region.

The number of males per 100 females in a population.

An area defined in the Australian Statistical Geography Standard (ASGS) designed as the smallest unit for the release of Census data. They generally have a population of 200 to 800 people, and an average population of about 400 people. SA1s in remote and regional areas generally have smaller populations than those in urban areas. SA1s are used as the building blocks for a number of ASGS defined regions including the Section of State, Urban Centre and Localities and Remoteness Structures. SA1s are also used to approximate a number of administrative regions such as Commonwealth and State Electoral Divisions. There are approximately 57,500 SA1s and they cover the whole of Australia without gaps or overlaps. Population estimates are prepared for SA1s by breaking down estimates from the SA2 level.

A medium-sized general purpose area defined in the Australian Statistical Geography Standard built from whole SA1s. Their purpose is to represent a community that interacts 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. SA2s generally have a population range of 3,000 to 25,000 people, and an average population of about 10,000 people. There are approximately 2,300 SA2s and they cover the whole of Australia without gaps or overlaps. SA2s are the base unit for preparing sub-state population estimates.

An area defined in the Australian Statistical Geography Standard built up from SA2s to provide a regional breakdown of Australia. SA3s aim to create a standard framework for the analysis of ABS data at the regional level through clustering groups of whole SA2s that have similar regional characteristics. Their boundaries reflect a combination of widely recognised informal regions as well as existing administrative regions such as State Government Regions in rural areas and Local Government Areas in urban areas. SA3s generally range in population from 30,000 to 130,000 people. There are around 360 SA3s and they cover the whole of Australia without gaps or overlaps.

An area defined in the Australian Statistical Geography Standard designed for the output of labour force data and to reflect labour markets. In rural areas SA4s generally represent aggregations of multiple 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. SA4s are built from whole SA3s. They generally have a population of over 100,000 people to enable accurate labour force survey data to be generated. There are 107 SA4s and they cover the whole of Australia without gaps or overlaps.

Usual residence within Australia refers to that address at which the person has lived or intends to live for a total of six months or more in a given reference year. For the 30 June reference date, this refers to the calendar year around it.

Preparation of estimated resident population (ERP) totals and age/sex breakdowns for areas within states and territories ('sub-state') uses data sourced from a variety of institutional environments. Much of this is administrative by-product data collected by other official organisations for purposes other than estimating the population.

Birth and death statistics are sourced from registration systems administered by the various state and territory Registries of Births, Deaths and Marriages. It is a legal requirement of each state and territory that all births and deaths are registered. Information about births is provided by the parent(s) of the child, while information about the deceased is provided by a relative or other person acquainted with the deceased, or by an official of the institution where the death occurred.

Estimates of internal migration are calculated using administrative data on changes of address from Medicare records and the Department of Defence in the case of the military. Medicare change of address data is provided to the Australian Bureau of Statistics (ABS) by Services Australia. Medicare is Australia's universal health insurance scheme and covers the large majority of Australians.

ABS Census of Population and Housing and Post Enumeration Survey (PES) data are used to determine a base population from which ERP is calculated. Census information is also used to estimate sub-state overseas migration. For information on the institutional environment of the ABS, including the legislative obligations of the ABS, financing and governance arrangements, and mechanisms for scrutiny of ABS operations, see ABS Institutional Environment.

ERP is the official measure of the population of areas in Australia according to a usual residence population concept. It refers to all people, regardless of nationality or citizenship, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. It includes usual residents who are overseas for less than 12 months out of a continuous 16-month period. It excludes those who are in Australia for less than 12 months out of a continuous 16-month period.

Sub-state estimates of the resident population as at 30 June are released annually for all Statistical Areas Level 2 (SA2s) and Local Government Areas (LGAs) in Australia. They are also available for other statistical areas as defined in the Australian Statistical Geography Standard (ASGS), including Non-ABS Structures such as Commonwealth and State Electoral Divisions.

There are legislative requirements for the ABS to provide population estimates. ERP plays an important part in the allocation of federal government funding to the local government authorities of Australia. ERP also assists in decisions regarding development, infrastructure (such as hospitals or schools) and policy formulation, monitoring and reporting. The geographic distribution of ERP informs on issues such as remoteness (access to services) and population density. The level and growth of ERP both reflects and affects economic, social and environmental issues. In addition, the age/sex composition of ERP informs discussion of issues such as population health, ageing and fertility.

Sub-state ERP is released annually with a reference date of 30 June. To meet the competing demands for accuracy and timeliness, there are several versions of these estimates. Preliminary estimates of sub-state population totals are available approximately nine months after the reference date and age/sex breakdowns are available about 14 months after the reference date. Revised estimates are available a year later (once revisions to births, deaths and net overseas migration at the state/territory level have been taken into account) and final estimates after the following Census.

All ERP data sources are subject to non-sampling error. Non-sampling error can arise from inaccuracies in collecting, recording and processing data. In the case of Census and PES data, every effort is made to minimise reporting error by the careful design of questionnaires, intensive training and supervision of interviewers, and efficient data processing procedures. The ABS does not have control over any non-sampling error associated with birth and death statistics (managed by the state and territory Registries of Births, Deaths and Marriages) or the Medicare data used for internal migration estimates (managed by Services Australia). The accuracy of Medicare data is largely dependant on the propensity of people who have moved to update their address details with the relevant government agency, and the time taken to do so.

Accuracy of sub-state ERP can be measured in Census years, when estimates updated from the previous Census can be compared with estimates from the current Census. For further information on accuracy see the Explanatory Notes of Regional Population Growth (cat. no. 3218.0).

The balance between timeliness and accuracy means that the user can choose more timely data (preliminary) or more accurate data (as revised or final data become available) depending on their needs.

The accuracy of sub-state ERP also depends on the accuracy of the independently and previously derived state and territory population estimates, to which it is constrained. The accuracy of state and territory ERP is described in the Quality Declaration for Australian Demographic Statistics (cat. no. 3101.0).

In recognition of the inherent difficulty in population estimation, population figures in commentary text published by the ABS are rounded. While unrounded figures are provided in summary tables and the detailed spreadsheets, accuracy to the last digit should not be assumed. Estimates of change in population are based on unrounded numbers.

Population estimates are prepared based on the Australian Statistical Geography Standard (ASGS). Estimates are released for Statistical Areas Levels 2 to 4 (SA2s to SA4s) and Greater Capital City Statistical Areas (GCCSAs), as well as other ABS and Non-ABS Structures, including Local Government Areas (LGAs). For more information on the geographic regions of the ASGS see Australian Statistical Geography Standard (ASGS): Volume 1 - Main Structure and Greater Capital City Statistical Areas, July 2016 (cat. no. 1270.0.55.001).

Population estimates based on the concept of 'usual residence' have been produced for sub-state regions since the 1970s. Prior to this, sub-state population figures were calculated on the 'actual location' concept - that is, based on the number of persons actually present at that location at the given time. Estimates based on actual location are generally higher in areas which attract short-term migrants, such as tourist areas, and it is important to note this break in time series when comparing historical population estimates.

Prior to 2017, intercensal sub-state ERP was prepared using regression models, whereby change in population was modelled based on changes in indicator data sources (dwelling approvals, Medicare enrolment counts and counts of people on the Australian Electoral Roll). From 2017 onwards, estimates have been prepared using the component method, whereby ERP is prepared by adding natural increase (births minus deaths) and net migration occurring over a period to the population at the beginning of the period. While this is a significant change in the method used to estimate population change out from Census-based estimates, it is not considered a break in time series. The method used to estimate intercensal ERP shapes rebased intercensal population change, however the end points reflect what the previous and most-recent Censuses have shown for each area. Under the old regression method, new models were prepared every five years based on what was learnt from the last two Censuses. Therefore, under a regression- or component-based approach, the estimation process is reset every five years.

The sub-state birth and death statistics in this publication are not consistent with those found in Births, Australia (cat. no. 3301.0) and Deaths, Australia (cat. no. 3302.0), which are presented according to calendar years and have a different scope. The birth and death statistics contained in this publication are for financial years, to correspond with the 30 June reference date for sub-state ERP.

ERP is generally easy to interpret as the official measure of Australia's population on a place of usual residence basis. However, there are still some common misconceptions. For example, a population estimate uses the term 'estimate' in a different sense than is commonly used. Generally the word estimate is used to describe a guess or approximation. Demographers mean that they apply the demographic balancing equation by adding births, subtracting deaths and adding the net of overseas and internal migration to a base population. Each of the components of sub-state ERP are subject to error, but ERP itself is not in any way a guess. It is what the population would be if the components are measured well. 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).

Regions are ranked by both largest growth and highest growth rate. Largest growth is based on the absolute change in population between 30 June of the base year and 30 June of the reference year, while highest growth rate is based on the percentage change. Regions with ERP of less than 1,000 people in the base year are excluded from the highest growth rate rankings due to the volatility of percentage changes when calculations are based on small numbers. Due to the volatility of small-area population estimates, rankings should be considered indicative of relative growth between areas within each state and territory, not definitive.

Annual population estimates at 30 June for all SA2s and LGAs in Australia are made freely available on the ABS website in a variety of formats. Key figures are also presented in the commentary accompanying this release. A list of related ABS releases that may be of interest to users of these estimates can be found in the Explanatory Notes.

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