Methods
This section provides key information about the methods used in this report.
Age
In this report, numbers of young people in detention include all age groups unless otherwise specified. Population rates include young people aged 10–17 only (see Rates).
The age on an average night each quarter is calculated based on the age a young person is each night that they are in detention. If a young person changes age during a period of detention, then the average nightly number in detention will reflect this.
For example, where a young person turns 18 during a period of detention, any nights spent in detention (sentenced or unsentenced) aged 18 will be counted only in quarterly average nightly population for the 18+ age group. Similarly, nights spent in detention before a young person has turned 18 will be counted only in the 10–17 age group.
Average nightly data broken down by age are not comparable to Youth detention population in Australia releases prior to 2020. For more information, see Report editions.
Average nightly population
The average nightly population is calculated by adding the duration (in nights) of each period of detention that falls within the quarter and dividing the summed duration by the number of nights in the quarter.
Indigenous status
Information on Indigenous status has been collected since the implementation of the Youth Justice National Minimum Data Set (YJ NMDS). The Australian Institute of Health and Welfare (AIHW) uses 'First Nations people' to refer to Aboriginal and Torres Strait Islander people in this report.
Nationally, the proportion of young people with ‘not stated’ Indigenous status was between 0.1% and 0.8% each quarter between the June quarter 2020 and the June quarter 2024. This proportion was low (7.1% or less each quarter) in all states and territories.
Changes in the collection and recording of Indigenous status can affect rates of First Nations identification over time.
There are some differences in the ways states and territories collect information about Indigenous status. Not all jurisdictions use the national standard question and standard codes for recording Indigenous status, as recommended by the Australian Bureau of Statistics. Some jurisdictions have taken steps to improve their data collection forms and information systems in recent years to address this issue.
Legal status
Young people who are both sentenced and unsentenced at the same time (that is, serving multiple or concurrent supervision orders) are classified as ‘sentenced’ in this report.