QUALITY DECLARATION - SUMMARY
Preparation of the estimated resident populations (ERPs) for areas within states and territories ("sub-state") uses data sourced from a variety of institutional environments. Much of the data is administrative by-product data collected by other organisations for purposes other than estimating the population.
For more detail, please read Institutional Environment (full version).
The 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. It excludes overseas visitors who are in Australia for less than 12 months.
Sub-state estimates of the resident populations as at 30 June are released annually for all Statistical Local Areas (SLAs) and Local Government Areas (LGAs) in Australia and are available for other statistical areas as defined in the Australian Standard Geographical Classification (ASGC) and non-standard areas such as Postal Areas.
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 Areas of Australia and may assist in decisions regarding development (such as hospitals or schools) and policy making. The geographic distribution of ERP informs on issues such as remoteness (access to services) and population density. The level and growth of ERP for each LGA over time can reflect economic, social and environmental issues. In addition, the age/sex composition of ERP informs discussion of issues such as ageing and fertility.
Sub-state ERPs are released annually with a reference date of 30 June each year. To meet the conflicting demands for accuracy and timeliness there are several versions of sub-state/territory population estimates. Preliminary estimates of sub-state population totals are available approximately nine to ten months after the reference date and age-sex breakdowns are available about 12 months after the reference date. Revised estimates are available a year later (once revisions to births, deaths and net overseas migration have been taken into account) and final estimates after the following census. More timely data (preliminary) will not be as accurate as revised or final data. Releasing preliminary, revised and final ERP involves a balance between timeliness and accuracy.
All ERP data sources are subject to non-sampling error. Non-sampling error can arise from inaccuracies in collecting, recording and processing the data. In the case of Census of Population and Housing and the Census Post Enumeration Survey (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 Medicare and AEC data nor, to a large extent, dwelling approvals, births, deaths and overseas migration data. The accuracy of Medicare data and AEC data is largely dependant on the length of time taken for migrators to update their address details. However, there are methods in place that attempt to account for delayed birth and death registrations.
As discussed under Timeliness, the trade off 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.
Accuracy of sub-state ERPs is measured in census years, when both preliminary estimates (derived from updating the ERPs from the previous census) and final estimates (based on the current census) are prepared. Differences between these two sets of estimates are referred to as intercensal errors. An indication of the accuracy of ERPs can be gauged by assessing the size and direction of the intercensal errors. For further information regarding intercensal errors, see the Explanatory Notes of Regional Population Growth (cat. no. 3218.0).
The accuracy of sub-state ERPs is partly dependent on the accuracy of state and territory population estimates, to which they are constrained. The accuracy of state and territory ERPs is described in the Quality Declaration for Australian Demographic Statistics (cat. no. 3101.0).
In recognition of the inherent inaccuracy involved in population estimation, population figures in text and accompanying summary tables published by the ABS are rounded. While unrounded figures are provided in the detailed spreadsheets, accuracy to the last digit is not claimed and should not be assumed. Percentage change in population is based on unrounded numbers.
Annual population estimates for LGAs and/or SLAs have been published (not necessarily by the Australian Bureau of Statistics) for Victoria since 1875, New South Wales and Queensland since 1911, South Australia since 1915, Tasmania since 1923, Western Australia since 1926, the Australian Capital Territory since 1968 and the Northern Territory since 1981.
Population estimates based on the concept of "usual residence" have been produced for LGAs and/or SLAs since 1976. Prior to this, LGA 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.
Caution must also be exercised when comparing different ERPs on different ASGC boundaries. ASGC to ASGC concordances are produced by the ABS to convert historical data (on old boundaries) to the new ASGC boundaries, based on how many people are believed to reside in the affected Census Collection Districts. Historical data are readily available on current boundaries for all SLAs in Australia, back to 2001. Earlier sub-state ERPs on current boundaries may be available on request.
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. The demographic use of the word, when referring to sub-state ERPs (in a non-census year), means the result of a mathematical model, where relationships are established between changes in population and changes in indicators between the two most recent censuses for groups of SLAs. More detailed explanations of the concept of ERP, as adopted by the ABS for official population estimates, are contained in Information Paper: Population Concepts, 2008 (cat. no. 3107.0.55.006), Population Estimates: Concepts, Sources and Methods (cat. no. 3228.0.55.001) and Methods and Procedures for Estimating Small Area Populations in Australia (cat. no. 3121.0).
In text and data published by the ABS, LGAs are ranked according to ‘largest’ and ‘fastest’ growth in ERP. Largest growth is based on the absolute change in population between 30 June of the previous year and 30 June of the current year, while fastest growth is based on the rate of change in population (percentage change in population) for the same period. LGAs with estimated resident populations of less than 2,000 people at 30 June of the previous year are excluded from the fastest growth rankings due to the volatility of percentage changes when calculations are based on small numbers. Due to the inherent imprecision of small-area population estimates, rankings should be considered indicative of relative growth between LGAs within each state and territory, not definitive.
Annual population estimates at 30 June for all SLAs and LGAs in Australia are made freely available on the ABS web site. A list of related ABS releases that may be of interest to users of these estimates can be found in the Explanatory Notes of Regional Population Growth (cat. no. 3218.0).
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