Data use considerations
Age data, combined with sex data, is essential to produce accurate population estimates based on the Census count.
Age is used during processing as a cross check with other variables; for example, the age of the respondent determines whether particular questions asked in the Census are applicable.
Respondents occasionally make errors in reporting their age or date of birth, such as:
- reporting their last birthday or the date they filled out their Census form rather than their date of birth
- parents filling in the form on their children's behalf and inadvertently reporting their own age or date of birth for their children
- character transposition errors
- other typographical errors (e.g. sticky key repetition).
Character transposition and typographical errors are particularly relevant to the online version of the Census form.
Data captured from written responses carries a small risk of character recognition error, mainly caused by poor handwriting or respondents writing outside the question box. The vast majority of individual characters written on paper forms met pre-set recognition confidence levels and were accepted without further examination. Characters that failed given recognition confidence levels, or responses where there was a discrepancy of more than three years between age last birthday and date of birth, were sent to clerical officers for further determination based on visual inspection of an image of the response.
Other checks on age (such as unlikely combinations of age and other variables) were made at various stages during processing, to ensure an acceptable level of quality was maintained.
There are a small number of areas where there was a high level of non-response to the age question and age was imputed. The age distribution in areas where there are high levels of age imputation may not be representative of the underlying population and should be interpreted with caution. This is more noticeable in the small number of remote communities where there is a high level of age imputation (more than 20% of Census counts), combined with the reporting of Aboriginal and/or Torres Strait Islander status. The data for people where age was reported is not impacted.
Using the Imputation flag for age (IFAGEP), the non-response rate for Age (AGEP) was 4.4% in 2021. This is a decrease from 5.6% in 2016. For more information on imputation, see Census Methodology.