About Census Classifications
What is a Classification?
The Census gathers information on a number of topics about persons, families and dwellings.
Each topic is represented on the Census form by one or more questions, each of which collects information about a particular data item, commonly called a variable. For example, information about persons includes the topic 'labour force'. The variables associated with the topic 'labour force' include Hours Worked, Labour Force Status and Occupation.
A variable may take a range of values. For example, the variable sex can take the values 'male' or 'female'. The range of values available for a variable is referred to as its classification. Each value of a variable is referred to as a category, or class, of the classification. Thus sex has two categories, 'male' and 'female'. Often the name used for a variable is also used for its classification, as in the case of the variable sex.
For efficient computer processing, and for specifying the order in which the categories of a classification are presented in a table or report, the categories of a classification are recorded in computer records as numbers. For the variable sex, the category 'male' is represented by the code number '1', and the category 'female' is represented by the code number '2'. Typically a classification is defined by a list of category descriptions and their corresponding codes.
For example:
 | Classification/variable | Sex | |
| | | |
| Code | 1 | Male |
| | 2 | Female |
Computer processing of Census forms immediately following a Census is largely concerned with the allocation of appropriate codes from the responses to the questions on the form. When tables are generated from the coded Census file, the classifications making up the table are usually presented in terms of their category descriptions as well as, or in place of, their code.
The Census uses Australian standard classifications where available and appropriate. Examples of these are the Australian and New Zealand Standard Classification of Occupations (ANZSCO), First Edition, Revision 1 or the Standard Australian Classification of Countries (SACC), Second Edition, Revision 1. These Australian standard classifications are used as the basis for Census output classifications such as Country of Birth of Person which uses SACC. Australian standard classifications are reviewed on an irregular basis to reflect changes in Australian society. A summary of any changes to these classifications is provided in the section 'What's New for 2011 - New and Revised Classifications'.
Where an Australian standard classification is not available, classifications specific to Census variables have been developed. Examples of such Census classifications are Child Type and Method of Travel to Work. The categories of these classifications are reviewed prior to each Census. A summary of changes to Census variables is provided in the section 'What's New for 2011 - Summary of Changes to Variables 2006 to 2011'.
Each classification, or variable, listed in this dictionary has a mnemonic associated with it - for example, HIND for Total Household Income (weekly). Mnemonics are a convenient shorthand method of describing Census classifications when specifying output requirements. Each classification relates to either a dwelling (or household), family or person. The last character of the mnemonic indicates the unit to which the classification relates:
- D indicates a classification that records a characteristic of a dwelling;
- F indicates a classification that records a characteristic of a family; and
- P indicates a classification that describes a characteristic of a person.
For information on geographical classifications see Australian Statistical Geography Standard (ASGS).
Specifying Recodes and User Defined Fields
If the tables available in standard Census publications do not meet a user's needs, user defined customised tables can be created. Customised tables often require the use of recodes, tailored to the client's requirements which include re-grouping fields in a classification. More complex User Defined Fields (UDFs) are new fields that can be created based on conditions applied to existing fields. UDFs can be created from two or more fields in a database or can consist of mathematical functions.
A recode example:
Standard Labour Force Status Classification
1 Employed, worked full-time
2 Employed, worked part-time
3 Employed, away from work
4 Unemployed, looking for full-time work
5 Unemployed, looking for part-time work
6 Not in the Labour Force
& Not stated
@ Not applicable
V Overseas visitor
Recoded Labour Force Classification
1 Employed
2 Unemployed
3 Not in the Labour Force
& Not Stated
Explanation:
The recoded Labour Force Classification was recoded by:
- Grouping all employed persons (codes 1,2,3) to be one item called Employed;
- Grouping unemployed persons (codes 4 and 5) to be one item called Unemployed;
- Including Not in the Labour Force (code 6) and Not Stated (code &) as single items; and
- Excluding Not applicable and Overseas visitors from the recode.
This recode can now be used with other standard or recoded classifications.
A User Defined Field example:
- Selecting Enrolled Nurse from the Occupation Classification; and
- Creating a recode for age by grouping ages 25-40.
These two selections can be combined using a User Defined Field function and labelling this as 'Enrolled Nurses aged 25-40 years'.
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