Census of Population and Housing 1986: Australian Standard Classification of Occupations (ASCO) / Classification and Classified List of Occupations (CCLO): Link File

What is the ASCO/CCLO Link File?

Record Structure

Sampling errors associated with statistics produced from the ASCO / CCLO Link File

Download an .rtf version of documents related to the ASCO/CCLO Link File

What is the ASCO/CCLO Link File?

The 1986 Census of Population and Housing, which was conducted by the Australian Bureau of Statistics (ABS) on 30 June 1986, collected data on a range of social and demographic topics, including occupations of the employed labour force. Responses to questions on the occupation of employed persons were coded using the Australian Standard Classification of Occupations (ASCO). This classification replaced the Classification and Classified List of Occupations (CCLO) used for previous censuses.

The Australian Standard Classification of Occupations (ASCO)

The new Australian Standard Classification of Occupations has been developed as a joint project by the Australian Bureau of Statistics (ABS) and the Department of Employment and Industrial Relations (DEIR). Development of the first edition of the ASCO was a major undertaking between 1979 and 1985, and work is continuing to maintain and enhance the classification.

The purpose of ASCO is to identify a set of occupations covering all jobs in the Australian economy; to define those occupations in terms of a number of selected attributes; and to group those occupations on the basis of their selected similarity into successively broader categories for purposes of statistical description and analysis.

Thus ASCO is a hierarchically structured classification based on the concept of type of work, defined primarily in terms of skill. The concept of skill is represented in ASCO by two distinct criteria: skill level and skill specialisation. The skill level of an occupation is a function of the amount of formal education, on-the-job training and previous experience usually necessary before an individual can satisfactorily perform the set of tasks involved. The skill specialisation of an occupation is a function of the field of knowledge required, tools or equipment used, materials worked on and goods and services produced in relation to the tasks performed.

This classification groups occupations on the basis of their similarity in terms of the above criteria. ASCO has four distinct levels of aggregation:

  • 8 major groups
  • 52 minor groups
  • 282 unit groups
  • 1079 occupations
Major groups are:

  • the broadest level of the classification
  • denoted by 1 digit codes
  • distinguished from each other on the basis of skill level
Minor groups are:

  • subdivisions of the major groups
  • denoted by 2-digit codes (the relevant major group code, plus an additional digit)
  • distinguished from other minor groups in the same major group on the basis of broadly stated skill specialisation
Unit groups are:

  • subdivisions of the minor groups
  • denoted by 4-digit codes (the relevant minor group code, plus 2 additional digits)
  • distinguished from other unit groups in the same minor group on the basis of a finer degree of skill specialisation
Occupations are:

  • subdivisions of the unit groups
  • denoted by 6-digit codes (the relevant unit group code, plus 2 additional digits)
  • distinguished from other occupations in the same unit group on the basis of detailed skill level and specialisation, and involve the performance of a common set of tasks.
The following example illustrates these conventions:

Major group 2Professionals
Minor group28Artists and related Professionals
Unit group2805Designers and Illustrators
Occupation2805-13Graphic Designer

The distribution of major, minor, unit groups and occupations used in the ASCO are as follows:

Major groupsMinor groupsUnit groupsOccupations
1. Managers and Administrators62160
6.Salespersons and Personal Service Workers62082
7. Plant and Machine Operators, and Drivers440162
8.Labourers and Related Workers534124

For a more detailed discussion of the conceptual basis of ASCO and a definition of the structure of major, minor and unit groups, see Part 1 of the Australian Standard Classifications of Occupations (ASCO): Statistical Classification (1222.0).

The Classification and Classified List of Occupations (CCLO)

The CCLO was used to code occupation data for censuses between 1961 and 1981 inclusive. This classification was originally adapted from the International Standard Classification of Occupation (ISCO), issued in 1958. ISCO was considerably revised in 1968, and the changes made were considered carefully in revising the CCLO for use at the 1971 Census.

The structure of the CCLO was based primarily on the type of the work performed. However, this criterion was interpreted in different ways in different segments of the classification. For example, in various parts of the classification, sex, industry, occupational status and qualifications are used as classification criteria.

In the CCLO there were three hierarchical levels to which census occupation statistics were aggregated. In 1981, the CCLO contained:

11 major groups, represented by a one or two digit numerical code;

73 minor groups, shown by numerical alphabetic codes; and

389 unit groups into which occupations were classed, with codes ranging from 001 - 865. Codes 866-870, which appear on the file, are for ABS internal use and should be ignored.

For further information about the CCLO, see Census 81 - Occupation (2148.0) or Index of Occupations, Australia (1211.0).

Establishing a link between ASCO and CCLO

To facilitate the comparison of occupation data between the 1986 Census and previous censuses, the ABS has developed a quantitative relationship linking the two occupation classifications. Such a quantitative link is necessary because it is not possible to map the new classification onto the old classification at a conceptual level because the philosophical basis of the two classifications is very different.

In the 1986 Census, data on occupations were collected from employed members of the labour force. For the census, the labour force was defined as persons aged 15 years or more who were either:

(a) employed; that is, persons who

(i) worked for payment or as an unpaid helper in a family business during the week prior to census night; or

(ii) had a job from which they were on leave or otherwise temporarily absent (including on strike or stood down) during the week prior to census night;


(b) unemployed; that is, persons who did not work and did not have a job but were actively looking for work during the four weeks prior to census night.

A job in any given establishment is a set of tasks designed to be performed by one individual. An occupation is a set of jobs with identical sets of tasks. Of course, every job is a little different and, in practice, an occupation is a collection of jobs sufficiently similar in their main tasks to be grouped together for classification purposes. ASCO occupation definitions list the sets of tasks which are common to all jobs in any given occupation.

Two questions on the census form (questions 29 and 30) were used to assist in coding of occupation for the 1986 Census. Question 30, which asked for a description of the main tasks a person performs in his/her occupation, was introduced for the 1986 Census to provide extra details required to code responses to ASCO. Only question 29 was used in coding occupation responses to CCLO to achieve consistency with past censuses.

For the first time in the processing of an Australian census, a micro-computer based computer assisted coding system using structured coding techniques was used for the coding of responses to occupation questions to ASCO. Coders were required to enter at least the first three letters of all words in the response given to the title question (Question 29). This data was entered in 'inverted form', with the main keyword, called the 'basic word', entered first and followed by the 'qualifying word' e.g. labourer builder's.

The computer displayed on the screen a list of possible matches with the keyed-in data. If there was a match with the occupational title, the displayed code would be recorded. Otherwise the coder would be guided by the computer through a series of matching actions drawing on the responses to the task, industry and employer questions (questions 30, 31 and 32). The code corresponding to the closest match on all relevant data items was recorded.

All CCLO coding was performed clerically as done in past censuses using the procedures and the classification as defined in the Classification and Classified List of Occupations (1206.0).

It should be noted that CCLO codes are not available in any other standard or special output from the 1986 Census.

The file is released in accordance with a Ministerial Determination (Statutory Rules 1983 No. 19) in pursuance of Section 13 of the Census and Statistics Act 1905. As required by the Determination, the ASCO/ CCLO : Link File has been designed so that the information on the files does not enable the identification of the particular persons to whom it relates. The classificatory detail for most items of data contained on the ASCO/ CCLO: Link File has been reduced in order to ensure that the confidentiality of individuals is protected.

In pursuance of Clause 7, the Determination requires clients to sign a Form of Undertaking stating that the information will be used for statistical purposes only.

Dimensions of the data set

The Link File consists of 264,588 logical records, one for employed person selected according to the sampling frame. Each logical record is one physical record in length.


To provide a basis for converting distributions of occupations coded to ASCO to distributions of occupations coded to CCLO, and vice versa, a quantitative link has had to be developed. The ASCO / CCLO Link File was created for the purpose of allowing users to create their own empirically derived link between occupation data produced in previous censuses and occupation data coded to ASCO in the 1986 Census.

For the census, this link was developed by coding responses to the occupation questions for a sample of employed persons to both occupation classifications (ASCO and CCLO). The final file consists of a 5 per cent sample of employed persons in all States and Territories (except NSW, where only 2 per cent were sampled). The sample was chosen by selecting every fourth collection district and every fifth dwelling within it. Non-private dwellings and caravans in parks and unoccupied dwellings, if selected, were included in the sample. In NSW, a third stage of sampling was introduced with a sampling fraction of 40 per cent, that is, of every five dwellings selected in the second stage, two were retained in the sample.

The following table shows the structure of the sample on a State/Territory basis.

State / TerritoryNo. of persons% of employed labour force

As the ASCO/ CCLO: Link data have been produced using sampling methods, the estimates given in the tables are subject to sampling error. See the section of this document "Sampling errors associated with statistics produced from the ASCO / CCLO: Link File" for more information.

Note on categories : Totals for the categories 'not stated' and 'inadequately described' are significantly larger in the ASCO than in the CCLO. ASCO is very precise in the definition of its categories at the unit group level. Unit groups in ASCO are defined in terms of skill level and skill specialisation and distinction between these groups can be more difficult to make on the basis of information obtained from household-based censuses and surveys.

Responses which are not sufficiently detailed to be coded to the unit group level of ASCO are coded to minor or major group levels as appropriate. For example, the title response 'Clerk' combined with a description of the main tasks as 'Clerical duties' would be assigned a code of 5000, indicating that the response was only able to be coded to the major group level of ASCO. In ASCO, n.e.c. groups are reserved for precisely defined occupations which are not sufficiently numerous in the labour force to be allocated a specific unit group code. They are not used as a means of processing poor quality data. For further information see the Australian Standard Classification of Occupations (A SCO) : Statistical Classification (1222.0).

The CCLO contains more broadly defined groups throughout the classification which allows for the coding of poor quality responses to the unit group level. Examples of some of these broadly defined groups in CCLO are given below:

CCLO CodeDescription
119Employers, workers on own account, directors, managers, n.e.c.
154Clerical workers, government n.e.c.
155Clerical workers, non-government n.e.c.
203Proprietors, shopkeepers, workers on own account n.e.c., retail and wholesale
743Other labourers n.e.c.
746Foremen (so described) n.e.c.
827Other ranks, Australian Military Forces

Record structure

This file contains certain characteristics of persons selected in the link sample, and allows the generation of a matrix of cells in which the two occupation codes (and the comparisons between them) can be cross-classified by a number of other variables (data items).

For each record on the ASCO / CCLO:Link File there are 11 fields containing a total of 19 characters, plus a field containing the weight which should be used when aggregating the raw data. The particular weight on each record varies depending on State and section of State (i.e. rural/urban). This weight field, of length 9, has an implied decimal point following the second digit. A list of weights used appears below.

The record structure for the link file is as follows:

Mnemonics used to define data items are detailed in the document "Data Items and Codes for the Census 86 ASCO / CCLO Link File".

Weights applied to the data

Weights for the ASCO/CCLO:Link File which have been provided on each record are as follows:



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