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Age (AGEP)

Census of Population and Housing: Census dictionary
Reference period
2021

Definition

This variable collects each person's age. If age is not reported, it is imputed. See Imputation flag for age (IFAGEP). For infants aged less than one year, 0 years of age is recorded.

Data is also available in 5 year groups (AGE5P) and 10 year groups (AGE10P).

Scope

All persons

Categories

CodeCategory
000-1150 to 115 years of age singly

Number of categories: 116

Question(s) from the Census form

What is the person’s date of birth and age?

What is the person’s date of birth and age?
What is Person 1's date of birth?

If date of birth is not known, please select 'Don't know date of birth' and provide Person 1's age.

More information

Day Month Year

OR

Don't know date of birth

Age
Age example
What is Person 1's date of birth?

If date of birth is not known, please select 'Don't know date of birth' and provide Person 1's age.

More information

Day Month Year

OR

Don't know date of birth (selected response)

Age years

Example

Age example

Example

What is Person 1's date of birth?

If date of birth is not known, please select 'Don't know date of birth' and provide Person 1's age.

More information

Day Month Year
18 March 1993

OR

Don't know date of birth

Age
28 years

More Information

Additional information relating to the question on: What is the person’s date of birth and age?

More Information

What is Person 1's date of birth?

If date of birth is not known, please select 'Don't know date of birth' and provide Person 1's age.

More information

It is important to note:
• Date of birth is the date that the person was born.
• Age is required only if the person's date of birth is not known. Please report age at Census night – Tuesday 10 August 2021.

If the person is less than one year old and their date of birth is not known, enter '0' in the age box.

How this variable is created

Age is calculated from date of birth when provided, otherwise stated age is used. Where both sets of information are provided, date of birth is used to derive an age in years, except in circumstances where errors in the date of birth are identified. Age data is only output in whole years.

Where a respondent does not answer the age question, age is imputed using other information on the form and using an age distribution of the population. Where respondents report an age outside the acceptable range or where there were inconsistencies between age and relationship data, age is also imputed. For more information about imputation, please see imputation in the Census Glossary.

The Imputation flag for age (IFAGEP) variable indicates if a person's age was imputed in the Census.

History and changes

A question relating to age has been asked in every Census since 1911. Since 2006, respondents have had the option to report either date of birth or age in years.

For 2021, question wording changed from 'or' to 'and' in both the question wording and response area. The online form has been changed to primarily ask for date of birth (DOB) and the respondent is presented with a check box if DOB is not known so that they can enter the person’s age. This is to encourage the provision of more accurate data.

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.

Related variables and glossary terms

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