The Australian Standard Geographical Classification (ASGC) is a classification used by the ABS for the collection and dissemination of geographical statistics. It incorporates several hierarchies of geographic areas (also referred to as spatial units) and defines the individual structures and the area types of which each structure is composed. Each geographic area in the classification is identified by an unique numeric code.
Purpose of the classification
The ASGC is a system for the classification of statistical units by geographical areas. The main purpose of the ASGC is for collection and dissemination of geographically classified statistics. These are statistics with a 'where' dimension.
The ASGC is an essential reference for users to understand and interpret the geographic context of ABS statistics. The ASGC divides Australia into six different hierarchies of geographical areas to suit different statistical purposes. The spatial units of some hierarchies (the Main Statistical Region and Section of State) aggregate to all of Australia, while some hierarchies (the Local Government Area, Statistical District and Urban Centre/Locality) cover only a part of Australia of particular statistical significance. The ASGC provides a common framework of statistical geography and enables the production of statistics which are comparable and can be spatially integrated.
In practice, statistical units such as households and businesses are first classified or assigned to a geographical area in one of the six ASGC structures. Data collected from these statistical units are then compiled into ASGC-defined geographic aggregations which, subject to confidentiality restrictions, are then available for publication.
Units of the ASGC
Common types of statistical units classified are households in population censuses and surveys, and establishment locations (eg individual farms, mines, factories and shops) in economic censuses and surveys. Once these units have been classified and assigned ASGC codes, statistics can be compiled and published (subject to normal confidentiality restraints) for the geographical areas in which the units are located.
Nature of the classification
The ASGC Structural Chart depicts the ASGC in terms of its six structures. The spatial units for the structures of the ASGC are as follows:
- States and Territories are the largest spatial units in the ASGC. Six States and five Territories are included: New South Wales, Victoria, Queensland, South Australia, Western Australia, Tasmania, Northern Territory, Australian Capital Territory, Jervis Bay Territory and the external territories of Christmas Island and Cocos (Keeling) Islands.
- Statistical Divisions (SDs) are large, general purpose regional type spatial units used widely in the compilation of ABS statistics. SDs are an aggregate of Statistical Subdivisions (SSDs), and Statistical Local Areas (SLAs), and in turn make up each State and Territory. They do not cross State or Territory boundaries, except in the case of the Other Territories SD which comprises the Jervis Bay Territory and the Territories of Christmas Island and Cocos (Keeling) Islands.
- Statistical Subdivisions (SSDs) are general purpose spatial units of intermediate size between the SLA (smaller) and the SD (larger) in the ASGC Main Structure. SSDs also aggregate to Statistical Districts in the Statistical District Structure.
- Statistical Local Areas (SLAs) are the base spatial units used to collect and disseminate statistics other than those collected from the Censuses of Population and Housing. In non-census years, the SLA is the smallest unit defined in the ASGC for statistical purposes. In census years, an SLA consists of one or more whole Collection Districts (CDs). In aggregate, SLAs cover the whole of Australia without gaps or overlaps.
SLAs are based on the boundaries of incorporated bodies of local government where they exist. These bodies are the Local Government Councils and the geographical areas which they administer are known as Local Government Areas (LGAs). SLAs can be whole or part LGAs. In the remainder of Australia where there is no incorporated body of local government, SLAs are defined to cover the unincorporated areas. At 1 July 1998 there are 1,332 SLAs in Australia.
- Census Collection Districts (CDs) are designed for use in the census years for the collection and dissemination of Census of Population and housing data. They are not current at other times. The CD is the smallest spatial unit of the ASGC. CDs aggregate directly to form the larger spatial units of SLAs, Sections of State (SOS) and Urban Centre/Localities. In aggregate, CDs cover the whole of Australia without gaps or overlaps. For the 1996 Census, 34,500 CDs were defined throughout Australia.
- Local Government Areas (LGAs) consist of one or more SLAs and cover only incorporated areas of Australia. Incorporated areas are legally designated areas such as cities, towns and shires, over which incorporated local governments have responsibility.
- Major Statistical Regions (MSRs) cover the whole of Australia without gaps or overlaps. They do not cross State/Territory boundaries (except in the case of Other Territories) and serve the same purpose as Statistical Regions, but at a broader level. The larger States are dissected into two MSRs but because of population size, Tasmania, Northern Territory, Australian Capital Territory and Other Territories each have only one MSR defined.
- Statistical Regions (SRs) are designed primarily as sufficiently large regional type spatial units suitable for both population census and labour force statistics. Each SR consists of one or more Statistical Region Sectors.
- Statistical Region Sectors (SRSs) consist of one or more SLAs. They are used primarily for disseminating selected Population Census and Labour Force statistics.
- Statistical Districts (S Dists) are significant predominantly urban areas in Australia which are not located within a Capital City SD. The boundaries are designed to contain the anticipated urban spread of the area for at least 20 years. They are generally defined around one or more urban centres with a population of 25,000 or more. S Dists consist of one or more SSDs and can straddle State and Territory boundaries (e.g. Gold Coast-Tweed S Dist lies partly in Queensland and partly in New South Wales).
- Urban Centres and Localities (UC/Ls) are defined for each Census of Population and Housing and consist of one or more whole adjoining CDs with urban characteristics and represent, in the case of Localities, population clusters between 200 and 999 people, and in the case of Urban Centres, population clusters of 1,000 or more people. Because of their nature UC/Ls sometimes straddle SLA, LGA, SSD and other ASGC spatial unit boundaries. For statistical purposes, people living in Urban Centres are classified as urban while those in Localities are classified as rural.
Structure of the classification
- Sections of State (SOS) are defined for each Census of Population and Housing. Like the UC/L structure the SOS structure uses population counts from the latest Census of Population and Housing to define CDs between urban and rural. Unlike the UC/L structure, the SOS structure covers all of Australia. Each SOS represents an aggregation of non-contiguous geographical areas of a particular urban/rural type. The current SOS structure comprises the following categories: Major Urban, Other Urban, Bounded Locality, Rural Balance and Migratory.
The spatial units of the ASGC are arranged in several hierarchies. They indicate, for example, that Census Collection Districts (CDs), the smallest spatial units and area building blocks in the ASGC, form the lowest or most detailed hierarchical level of the classification. CDs aggregate, without gaps or overlaps, to Statistical Local Areas (SLAs) which in turn, represent another hierarchical level and aggregate without gaps or overlaps to Statistical Subdivisions (SSDs) etc.
It is not possible to fit all ASGC spatial unit types into a single hierarchy because some ASGC spatial unit types do not relate to each other in a hierarchical way. For example they cut across each other as is the case with some LGAs and SSDs. The structure of the ASGC reflects this in that it consists of six separate structures: the Main, LGA, Statistical District, Statistical Region, Section of State and Urban Centre/Locality. These structures can be seen in the ASGC structural chart below.
Although the ASGC is the principal Australia-wide geographical classification of the ABS, it does not, for technical and other reasons, incorporate all spatial unit types for which the ABS produces statistics in response to user needs. Data may also be classified according to postcode areas or electoral divisions.
The 1996 edition of the ASGC was used for the collection and dissemination of the 1996 Census of Population and Housing data. The latest edition of the ASGC (Edition 1998), is effective from 1 July 1998 and incorporates some changes to the 1996 spatial units, particularly in areas where there have been changes to Local Government Areas.
Further information may be obtained through the following publication:
- Australian Standard Geographical Classification (ASGC) (Cat. no. 1216.0)
Phone: (02) 6252 5888
Fax: (02) 6252 8666