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Upcoming Change to Methodology for Sub-State Population Estimates
Births and deaths data are provided to the ABS by state and territory Registrars of Births, Deaths and Marriages. The registration of births and deaths is compulsory in Australia under relevant state/territory legislation. This data is provided by age and sex and is geocoded to the required levels of the Australian Statistical Geography Standard (ASGS) for sub-state ERP production - namely Statistical Areas Level 2 (SA2s) and Local Government Areas (LGAs).
Regional internal migration estimates (RIME) are prepared using Medicare change-of-address data by age and sex, provided by the Australian Government Department of Human Services. Expansion factors are applied to account for moves by age and sex, state/territory and type of move (arrival or departure) known to be missing from the Medicare data (e.g. young adult males are less likely to update their details with Medicare). This data is supplemented with aggregated data on Australian Defence Force personnel movements, supplied by the Australian Government Department of Defence.
In the past, this Medicare data was converted from the postcode level to SA2 and LGA regions. For further information on this method, see Discussion Paper: Assessment of Methods for Developing Historical Estimates of Regional Internal Migration (cat. no. 3405.0.55.001). From 2017 onwards, the ABS will instead make use of Medicare data coded directly to the ASGS, significantly simplifying the method outlined in this paper.
The ABS has developed a model to estimate total overseas migration into and out of the regions, utilising what we know about population change from previous Censuses, and from the natural increase and RIME components. The main data source used to model these regional overseas migration estimates (ROME) is the Census. In particular, information on the number of overseas arrivals to regions, the proportion of the total population of a region born overseas and Socio Economic Indexes For Areas (SEIFA) scores for regions. These estimates can then be broken down into age and sex, utilising information from the Census and other data sources at the age and sex level.
Preparation and Release Schedule
The ABS will continue to release annual sub-state population estimates as at 30 June for regions of the ASGS including SA2s and LGAs. The method for Census year estimates will not change. That is, estimates will be based on Census counts of usual residence (excluding short-term overseas visitors in Australia), with an allowance for Census net undercount and Australian residents temporarily overseas at the time of the Census.
Estimates in non-Census years will be prepared by adding natural increase (births minus deaths) and net internal and overseas migration by age and sex to the base population. Each of these components, which are derived from the data sources discussed above, will be constrained to the corresponding state and territory estimates by age and sex released in Australian Demographic Statistics (cat. no. 3101.0) to ensure consistency between state and territory and sub-state population estimates.
The release of estimates prepared using the component method will not change, with totals released around 9 months after the reference date and age-sex breakdowns available roughly 13 months after the reference date. The first sub-state total population estimates prepared using this new method will be for 30 June 2017 and will be released in Regional Population Growth (cat. no. 3218.0) on 28 March 2018. In addition to the population estimates, each of the components of population change for SA2s and LGAs for 2016-17 will be included, allowing users to understand the main drivers behind population change for sub-state areas. Age-sex breakdowns of these estimates will then be released in late August 2018 in Population by Age and Sex, Regions of Australia (cat. no. 3235.0).
For further information on this new methodology, please contact the Regional Population Unit at email@example.com.
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