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Age in five year groups (AGE5P)

Census of Population and Housing: Census dictionary
Reference period
2021

Definition

This variable collects each person's age in five-year groups. 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.

Age is also available for 0 to 115 years singly (AGEP) and 10-year groups (AGE10P).

Scope

All persons

Categories

CodeCategory
010-4 years
025-9 years
0310-14 years
0415-19 years
0520-24 years
0625-29 years
0730-34 years
0835-39 years
0940-44 years
1045-49 years
1150-54 years
1255-59 years
1360-64 years
1465-69 years
1570-74 years
1675-79 years
1780-84 years
1885-89 years
1990-94 years
2095-99 years
21100 years and over

Number of categories: 21

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

      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

      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 variable (IFAGEP) 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). 

          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 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