Rates Information
Population estimates used for rates calculations
All rates in this report, including historical rates, have been calculated using population estimates based on the 2021 Census. All Indigenous population rates in this report are calculated using the Indigenous population estimates and projections, based on the 2021 Census.
Population rates
Crude rates are calculated using the Australian Bureau of Statistics estimated resident population (ERP) at the start of the range (for example, rates for 2011–12 were calculated using the ERP at 30 June 2011).
For SHS client groups, the calculation of population rates was based on the Australian estimated resident population at 30 June of the reference year for the age profile relevant to each client group. The age profiles used for each client group were:
- aged 10 and over: Clients who were exiting custodial arrangements, Clients with a current mental health issue, and Clients with problematic drug and/or alcohol use
- aged 12 to 24: Children and young people receiving support alone
- aged under 18: Clients on a care and protection order
- aged 18 and older: Clients who are current or former members of the Australian Defence Force
- aged 55 and older: Older clients
- all ages: clients with disability, clients leaving care, clients who have experienced family and domestic violence.
Age-standardised rates
Population rates were adjusted (standardised) for age to enhance the comparison between populations over time that have different age structures. Specifically, direct standardisation has been used where age-specific rates are applied to a standard population (the ERP as at 30 June 2001, unless otherwise specified). This effectively accounts for the influence of age structure on the calculated rate and is referred to as the age-standardised rate. In this publication direct age-standardisation has been used to compare Indigenous and non-Indigenous Australians (AIHW 2011).
Rate ratio
Rate ratios are mainly used to compare Indigenous and non-Indigenous rates and provide a measure of the level of Indigenous over-representation. A rate ratio is calculated by dividing the client rate for Indigenous Australians by the client rate for non-Indigenous Australians.
Average annual rates of change
The average annual rates of change or growth rates have been calculated as geometric rates:
Average rate of change = ((Pn/Po)^(1/n) -1) x 100
where:
Pn= value in the later time period
Po= value in the earlier time period
n = number of years between the 2 time periods.