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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 which seek 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 one of 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.
The 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 forms. 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 Standard Classification of Occupations (ASCO) or the Standard Australian Classification of Countries (SACC). These Australian Standard Classifications are used as the basis on which to build some census-specific classifications such as Birthplace of Individual which uses SACC. These Australian Standard Classifications are reviewed on an irregular basis to reflect changes in the Australian social environment. A summary of changes to some of these classifications is provided in the section ‘New and Revised Classifications’.
Where an Australian Standard Classification is not available, classifications specific to census variables have been developed. Examples of these classifications are Social Marital Status and Journey 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 ‘Summary of Changes to Variables — 1996 to 2001’.
Each classification, or variable, listed in this Dictionary has a mnemonic associated with it, for example, HIND for Household Income. 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 to which of these units the classification relates:
The classifications listed in this Dictionary do not include the geographic classifications used to describe the geographic areas covered by the Census. Geographic classifications formed by the aggregation of Collection Districts (CDs), such as Statistical Local Areas (SLAs), Local Government Areas (LGAs) and Electoral Divisions are described in the publication Statistical Geography Volume 2: Census Geographical Areas, Australia (Cat. no. 2905.0).
Additional geographic information can be found in Statistical Geography Volume 1: Australian Standard Geographical Classification (ASGC) 2001 (Cat. no. 1216.0).
If the tables available in standard census publications do not meet a user’s needs, user-defined (customised) tables can be created to meet specific user needs. Customised tables often require the use of recodes and defined fields.
Recoding is the process of aggregating certain categories within a classification into a user-defined category. The recode must be based on the standard categories within that classification. A recode is typically specified where a classification provides more detail than is required, in which case the client specifies a recode to regroup the full classification into broader categories. For example, a client may wish to group categories 3 to 7 in the Individual Income classification to provide one aggregated income range between $1 and $199. Some classifications such as Industry or Occupation are hierarchically structured and the client may specify that the data be output at the detailed (or 4 digit) level of the classification. Other clients may wish to collapse certain categories at the detailed level while still retaining the detailed level for other parts of the classification.
A defined field is a customised, or client-specified variable which is based on existing census variables. For example, a client may specify a defined field to combine a specific Occupation (eg. Enrolled Nurse) with certain categories of Age (eg. 25-40 years) to provide a customised variable. The client can then specify a title for the variable such as "Nurses aged between 25 and 40 years".
In most cases it is an easy process to order customised census tables and ABS Consultants are available to assist users in specifying the required recodes and defined fields.
In order to assist users to identify the classification of interest, topic and mnemonic indexes are provided. Note that you can use the Topic Index to chose and link you to classification details.