Technical notes

Data presented in the report and in the supplementary tables are mainly based on ‘clients’, with some data based on ‘support periods’ or ‘client groups’ (or ‘presenting units’—which identify clients who present together to a specialist homelessness agency, including clients who present alone—and receive a service). Information on clients who are homeless, at risk of homelessness or part of a group of special interest, is mostly client-level data and information on agencies, unmet demand and trends data is predominantly support period data.

The Australian Institute of Health and Welfare (AIHW) has strict confidentiality policies which have their basis in section 29 of the Australian Institute of Health and Welfare Act 1987 (AIHW Act) and the Privacy Act 1988 (Privacy Act). Cells in supplementary tables may be suppressed for either confidentiality reasons or where estimates are based on small numbers, resulting in low reliability. Information that results in attribute disclosure, (that is, if as well as being able to identify the entity, other details are revealed), will be suppressed unless agreement from the particular data provider to publish the data has been reached. Information on AIHW’s Privacy policy is available on the privacy page.

Population estimates used for rates calculations

All rates in this report, including historical rates, have been calculated using population estimates based on the 2016 Census. All Indigenous rates in this report are calculated using the Indigenous population estimates and projections, based on the 2011 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). Rates for 2018–19 data were calculated using the preliminary ERP at 30 June 2018.

Minor adjustments in rates may occur between publications reflecting revision of the estimated resident population by the Australian Bureau of Statistics.

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 Aboriginal and Torres Strait Islander 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 Australian 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


Pn= value in the later time period

Po= value in the earlier time period

n = number of years between the 2 time periods.