Age Standard

As one of the basic core demographic variables, age is most commonly used to differentiate populations in terms of the time elapsed (usually in complete years), from date of live birth to a specific point in time. It is widely used in cross classification with variables such as sex, marital status, and occupation and is collected in population statistics, surveys and administrative collections.

Age is an inherent attribute of an individual and (along with sex data) forms the basis of most analyses of the social and demographic characteristics of a population and should be asked across collections.

Many socio economic and demographic characteristics vary with age, for example, religious affiliation and marital status. These variables can be used in conjunction with age to assess and monitor service needs within a population. Data can also be collected on the age at death of deceased persons.

The standard term for the variable is 'Age'.

Age is defined as the measure of the time elapsed from date of live birth to a specific point in time, usually the date of the collection of the data. Age is an attribute of the counting unit 'person'.

Age is measured by calculating the time elapsed (usually in complete years) between date of birth and a specific point in time (e.g. date of a particular survey).

In 1982, The United Nations (U.N) set out provisional guidelines on standard international age classifications. Based on existing national practices and international recommendations, the U.N recommended the following:

• The development of international age classifications into 12 different subject areas available at three different levels of detail:
  • The highest level uses combinations of single and five year groupings ending on four and nine
  • The medium level uses combinations of five and ten year groupings
  • The lowest level consists of six broad population groups -comparable to infancy, youth, young adulthood, middle adulthood, older adulthood to average retirement and retirement (under 1, 1-14, 15-24, 25-44, 45-64 and 65 and over).
     

ABS practices align reasonably well with these guidelines as age output is generally in single, five or ten year age groupings. However, some ABS survey collections vary with legitimate reasons from standard age output categories. For example, the Labour Force Survey is restricted to persons 15 years and older, and surveys concerned with perinatal deaths require age in terms of minutes, hours and days.

Age may be measured in different 'time units'. Infants under one year are measured in minutes, completed days, weeks or months of life, while persons over one year are measured in complete years.

The classification of persons by age uses the calculated time unit 'in complete years'.

'Age' is a flat classification containing one level.

The standard categories are single, complete, calendar years from 000 to 104 and a category for 105 and over.

The code structure is 000 to 105. The examples below demonstrate the code structure applied to the Age classification:

000   0 years
001   1 year
002   2 years
...
010   10 years
011   11 years
012   12 years
...
103   103 years
104   104 years
105   105 years and over

Age has no provision for 'Not stated/Inadequately described' for ABS collections. In general, a 'best estimate' is provided for age, by derivation or imputation, based on other related variables in the questionnaire, or Any Responsible Adult (ARA) respondents. Data from sources (including administratively collected data), which have a 'Not stated' or 'unknown' code for Age may include a 'Not stated' category in output. Alternatively, the 'Not stated' response may be incorporated into totals, providing that the 'Total' is footnoted to show it includes these responses.

There are no residual categories associated with this classification.

There are no supplementary categories associated with this classification.

This variable has no coding indexes.

The variable 'Age' applies to all persons.

The 'Age' classification can be applied to other variables such as Age on Arrival, Age of Reference Person, etc.

In most collections, 'Age' can be derived from a single question.

The ideal question for most collections is:

For self enumerated questionnaires, the recommended format for the collection of age data is:

'Date of Birth' can easily be converted to completed days, weeks, months and years as required and it should be used wherever possible (see measurement issues).

In some collection methodologies this question may not be feasible and alternative questions are:

• Age last birthday?
• What was [your] [the person's] [(name)'s] age last birthday?
• What is [your] [the person's] [(name)'s] age in complete years?
   

Each question module may be accompanied by a brief explanatory note giving detailed instructions about how to answer the Age question. The explanatory note can be included with the chosen question module or in supplementary documentation. The explanatory note is in Appendix - explanatory script.

Age details can also be obtained from administratively produced data and can usually be derived using date of birth as this provides the best data quality. Age data are taken from the relevant records and documents such as school and employment data and hospital records. Because the manner in which age data is derived varies across administrative collections, it is recommended to use date of birth wherever possible.

For input categories, it is recommended that collections use 'date of birth' as the first preference and 'complete years' as the second.

Age should be stored at the most detailed level possible (date of birth or complete years) to provide flexibility in the cross classification with other variables, derivation of new data items, and production of output categories.

The standard output categories are aggregations of the input categories (the level at which age data are collected and stored).

The ABS recommends five or ten year age groups for most applications with cut off years varying according to the type of survey, or user requirements.

The recommended guidelines for developing output classifications for age are as follows:

• The recommended standard output classification should consist of five year groupings.
• Groupings with a range of more than five years should be in multiples of five years. It is important to ensure as many categories as possible are multiples of five years, or capable of aggregation to such groupings, to facilitate maximum comparability of age data from different sources.
• Groupings with a range of less than five years, including single years, should be capable of aggregation to five year groupings as subtotals.
• Subtotals of groupings, and groupings with a range of five years or more, should start at numbers ending with the digits '0' or '5' and finish in numbers ending with the digits '4' or '9'; for example, 15-19 and 20-24.
• The first group in any set of groupings should have a dash between two numbers (e.g. 0-4), not 'under' (e.g. under 5). Labels such as '4 years and under' are only acceptable under special conditions for example, data included in the first category do not necessarily span the full range of the standard category.
• The last group in any set of groupings should have the first number of the last age range followed by the words 'and over' (e.g. 75 and over), not the first number of the range followed by a '+' (e.g. 75+).
   

Certain circumstances may require output categories to vary from the recommended five and ten year groupings. For example, it may not be suitable for statistical data relating specifically to children or the elderly to use standard five and ten year groupings.

When developing output classifications or presenting age data, it is recommended to adhere to as many of the above guidelines as possible. However, it is not essential to adhere to these guidelines, if there are compelling reasons (e.g statistical) for deviating.

Guidelines for reporting 'Age' data in published tables are as follows:

• It is recommended, but not always appropriate for all totals in tables be labelled 'Total'. An exception is in life tables, as they show the calculated longevity of populations at particular ages, rather than counts or estimates.
• If 'Age' is used in the table stub, the stub heading should be labelled 'Age group' followed in brackets by the unit of time used. The following labels are recommended:
  • 'Age group (years)'
  • 'Age group (months)'
  • 'Age group (weeks)'
  • 'Age group (days)'.
     
• Units of time (e.g years, months, weeks, days) should not be mixed in table stubs unless a specific data collection requires it. For example, data relating to infant deaths may require a combination of time units such as minutes, hours, days or weeks.
• It is not acceptable to use a single category labelled '0' for infants under one year, as days, weeks or months rather than years are the appropriate time units for measuring the age of infants. If a single category is used, it should be labelled 'Under 1 year'.
• When survey scope restricts age ranges, output age groups should start at the beginning of the age range and finish at the end of the age range. For example, in a survey where the scope is persons 15-64 years the first age group should begin at 15 years and the last age group should end at 64 years and collections may need to use some age groups of less than five years. The first age grouping for a collection with a minimum age limit of two years should be '2-4 years', followed by standard five year age groups such as '5-9 years', '10-14 years' etc.
• The use of an open ended age group at the top of the age range is acceptable when presenting 'Age' output (e.g. '75 and over', '85 and over', etc.) provided there is an adequate sample size to support the group.
• Data from sources which have a 'Not stated' code for 'Age' may include a 'Not stated' category in the table. Alternatively, the 'Not stated' response may be incorporated into totals, providing that the 'Total' is footnoted to show it includes these responses.
   

The age categories below are the recommended output categories, however flexibility with groupings is allowable depending on purpose, scope or source of data.

The recommended standard output categories (excluding Labour Force Surveys) for five year groupings are:

0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90-94
95-99
100-104
105 and over
Total

The recommended standard five year groupings begin at '15' and end at '85 and over'. The in-scope population for Labour Force Surveys includes persons over 15 years of age with a cut off age of 85 years.

15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85 and over
Total

The recommended standard output categories for administrative collections are in five year groupings, as follows:

0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90-94
95-99
100-104
105 and over
Total

Output produced from the ABS Census uses the above standards as appropriate. However, the highest age for Census output for single years is 115 years.

The standard ten year output categories commence with a five year grouping of 0-4 years followed by ten year groupings beginning at five years. It is the only situation where a combination of five and ten year groupings is recommended. The recommended standard ten year categories are:

0-4
5-14
15-24
25-34
35-44
45-54
55-64
65-74
75-84
85-94
95-104
105 and over
Total

Variations to the recommended five and ten year groupings are required by some collections. For example, statistical data relating to children, perinatal deaths and the elderly require specific output categories.

Variations to the recommended standard output categories are acceptable if there are compelling reasons for doing so and if they adhere to the general rules for age output groupings. For example, some administrative collections may require output in single year of age such as collections related to childhood and for collections relating to deaths (excluding fetal and neonatal), the first grouping should be 'Under 1 Year'.

Although there are no strict statistical rules, there are some common principles involved in setting the number and range of age groups. These principles are as follows:

• for statistical applications the maximum number of groups should be related to the sample size and the reliability of the data. For confidentiality and reliability reasons a minimum number of responses are required in any category or cell before data can be published.
• the number of categories should be manageable and meaningful. The number of groups used should be no more than required to satisfy the intended purpose.
• the groupings should not distort the data. Inappropriate groupings can give the impression of an even spread of ages within a group when this is not the case. For example, a ten year grouping of 10-19 years could inadvertently give the impression that the data is spread evenly between 10 and 19 years when in fact most of the data may be clustered between 10-14 years or 15-19 years.
• age data should always be stored at the lowest 'time unit' so that aggregation can be made to single, five and ten year age groups, if required.
• collection of age data using age groupings should be avoided.
   

Collecting actual date of birth gives the best data quality. Collecting age in complete years can lead to an error where a respondent may round off or approximate their age in complete years. For example, a respondent born in June 1980 may respond to a survey in March 2012 that he/she is 32 years old when the more accurate 31 years could be obtained from date of birth.

There are no related classifications applicable to this variable.

This release previously used catalogue number 1200.0.55.006.