Population estimates
Estimates of the First Nations population used in the calculation of population rates
Australian Bureau of Statistics (ABS) estimates of the Aboriginal and Torres Strait Islander population are used in the calculation of population rates for many measures used in AIHW and other national reporting. The population rate is a measure such as the number of hospitalisations (numerator) expressed as a fraction of the total population (denominator).
Every five years, following each Census, the ABS recalculates the estimated resident population (ERP) of First Nations people, along with an updated time series population trend for previous periods ('backcast') and for forward periods ('projections') based on the best available demographic information (for example, births, deaths and migration) and forward assumptions of demographic change.
In late July 2024, the ABS released 2021 Census-based estimates of the First Nations population.
Previously, following the 2016 Census population rebase, the AIHW used 'backcast' estimates of the First Nations population to calculate population rates.
However, between 2016 and 2021, the Census-based Aboriginal and Torres Strait Islander population estimates increased by around 25%, with less than half of this increase (around 44%) due to demographic factors (births, deaths and migration). The remaining increase (around 56%) was due to other (non-demographic) factors, including changes in the propensity of people to identify as an Aboriginal and Torres Strait Islander person.
Due to the large non-demographic change, there are concerns about using the 2021 Census-based backcast populations for historical reporting, as follows.
Potential for a numerator/denominator bias in historical rates
This may result when the backcast population estimates include large numbers of people who have not identified as an Aboriginal and Torres Strait Islander person in the numerator data. As a result, historical rates may be artificially deflated.
Plausibility of rates for younger age groups
A large proportion of non-demographic change recorded by the ABS was among young people and this seems to be affecting the 2021 Census-based backcast population results. For example, the 2021 Census-based backcast estimates suggest that the population of Aboriginal and Torres Strait Islander children aged under 1 declined between 2011 and 2021. This is in contrast to trends in registered births of Aboriginal and Torres Strait Islander babies which increased over this period.
At the time of the 2024 report publication, discussions were underway across government agencies to agree on the most appropriate denominators to use. Pending a decision on this, the 2024 report used the 2016 Census-based population backcast estimates and forward projections as the source of denominator for analysis of population rates that includes numerators prior to 2021.
The current (2025) report has adopted the approach subsequently agreed upon by the Productivity Commission, AIHW, and ABS, which is that 2021 Census-based backcast estimates and projections be used as the denominator for rates. For the analysis in this report, the time trends have been limited back to the year 2016, due to the extent of non-demographic change.
This limitation was not applied to the MBS audiology rates, which used the 2024 weighted VII (Voluntary Indigenous Identifier) data. As indigenous identification at the latest time period was effectively ‘backcast’ to the earlier periods by the VII weighting methodology, longer time trend (prior to 2016) analysis was possible.
Please note that any comparison of population rates between the current and previous reports must consider the differences in population backcasts.
Each data table includes a footnote indicating the source and reference period of the population estimates used.
| Data tables | Analysis in the report | Population estimates used |
|---|---|---|
Newborn hearing screening (2.1.1a–b) Health checks (2.2a–a & b) HAPEE checks and diagnosis (2.4.1a–b, 2.4.2a–c) Hearing Australia clients (4.1a–d) EarTrain participants (5.3b–c) | Point-in-time, single year (calendar or financial) July 2021 or later | 2021 Census-based population estimates and projections |
Deadly Ears analysis 2022–24 (1.2.4a–b) Newborn hearing diagnosis 2022–24 (2.1.2) Emergency visits Jul 2022–Jun 2024 (3.1a–d & f–g) Hospitalisations Jul 2022–Jun 2024 (3.2a–e & g–j) Ear procedures Jul 2022–Jun 2024 (3.3.1a–d & f–g) Middle ear procedures Jul 2022–Jun 2024 (3.3.2a–c & e–g) Adenoidectomies Jul 2022–Jun 2024 (3.6a–c) | Point-in-time, multiple years combined All July 2021 or later | 2021 Census-based population estimates and projections |
Health checks (2.2b) Emergency visits (3.1e) Hospitalisations (3.2f) Ear procedures Jul 2021–Jun 2023 (3.3.1e) Middle ear procedures Jul 2021–Jun 2023 (3.3.2d) Adenoidectomies Jul 2021–Jun 2023 (3.6d) | Time series, single year (calendar or financial) Starting before July 2021 | 2021 Census-based population estimates and projections. |
Audiology services (2.3a–e) | Point-in-time or time series using the 2024 MBS VII weighted file | Use 2021 Census-based population estimates and projections. |
Reported ear and hearing problems, reported and measured hearing loss (1.1a–f, 1.2.1a–c, 1.2.2a–c, 1.2.3) Newborn hearing screening (2.1.1a–b) Waiting times (3.4.1a–e, 3.4.2a–e) Hearing Australia clients (4.1.1e–g, 4.1.2a–d) NDIS tables (4.2a–i) Audiologist etc and ENT workforce (5.1a–d, 5.2a–c) EarTrain participants (5.3a & d) HEBHBL (5.4a–c) | Analysis not requiring Census-based First Nations population estimates and projections | No action required |