Changes to Geographic Areas Between Censuses
Collection District (CD) boundaries can change for each Census, whereas Australian Standard Geographical Classification (ASGC) areas and non-ABS administrative boundaries can change every year. As a result information on changes to geographic areas is essential for time-series analysis.
Changes to Collection Districts
CD boundaries are re-defined each census according to a range of criteria. In general, CD design aims to produce convenient areas for a single collector workload. CD design thus involves splitting of CDs where there has been strong growth. Where population numbers are known to have declined, CDs may be amalgamated. Adjustment of the boundary between CDs may occur because of the need to respect other boundaries, such as Local Government Area (LGA) or suburb.
Unlike the 1996 Census, for 2001 there was no obligation for designers to split CDs which were expected to reach an upper limit of 400 dwellings. However, CD design was required to take into account the difficulty of collecting in an area. This can be influenced by the physical nature of the area and characteristics of the population, such as the percentage of residents who do not use English as a first language.
Approximately 80% of 1996 CDs were not redesigned for the 2001 Census. However, even where the geographic area for a 2001 CD has remained the same as it was in 1996, the CD may have a different CD code. Users who need to identify the 2001 equivalent for a 1996 CD should consult the 1996-2001 comparability listing.
The 1996-2001 comparability listing should also be used for information about the type of change which occurred and to relate the 1996 CD to 2001 CDs, for the 20% of CDs that were redesigned.
Comparability lists for 1991-2001 are also available.
2001 Census CD Comparability Lists
To assist users to compare data for CDs which changed between the 1996 and 2001 Censuses, a comparability code has been allocated to pairs of 1996 and 2001 CDs. The resultant listing, which includes all CDs for both 1996 and 2001, indicates the degree to which the boundary of a CD has changed between the 1996 and 2001 Censuses.
To assist users to compare data for CDs which changed between the 1991 and 2001 Censuses, pairs of 1991 and 2001 CDs have been assessed as either comparable or not comparable.
Users should note that there are a number of entries in the Comparability Lists where one of the pair of CDs is shown as having a CD code of zero. Zero CD Codes represent Shipping or Water CDs that have either been deleted or added for 2001 and therefore have no corresponding CD to be linked to in the other census year. In general this will not affect users as these CDs are excluded from most products.
The Comparability Lists are produced in 2001 Census CD order and can be purchased from the ABS for $81 (GST inclusive) per list. Note that a labour charge will be required in addition to the cost of the lists. A single digit comparability code is provided which indicates whether a CD is comparable between the 1996 and 2001 Censuses, and the 1991 and 2001 Censuses, as follows:
| Code | Description |
 | |
| 1991 - 2001 |
| |
| 0 | 2001 CD is comparable to the 1991 CD. |
| |
| 1 | 2001 CD is not comparable to the 1991 CD. |
| |
| 1996 - 2001 |
| |
| 0 | 2001 CD is perfectly comparable to the 1996 CD |
| |
| 1 | Although a change to the CD boundary has been made between the 1996 and 2001 Censuses, the 2001 CD is comparable as there is no change to population and dwelling counts due to boundary change. |
| |
| 2 | 2001 CD is comparable within a 2% dwelling or population limit. A boundary change has occurred, however no more than 2% of the dwelling or population counts in the 1996 CD have been subtracted or added. |
| |
| 3 | 2001 CD is comparable within a 10% dwelling or population change limit. A boundary change has occurred, however no more than 10% of the dwellings or population in the 1996 CD have been subtracted or added. |
| |
| 4 | 2001 CD is not directly comparable. A 1996 CD has been split into two parts, with the 1996 boundary containing two new 2001 CDs |
| |
| 5 | 2001 CD is not directly comparable as a 1996 CD has been split into 3 or more parts, with the 1996 boundary containing three or more new 2001 CDs. |
| |
| 6 | 2001 CD is not comparable because of splits, amalgamations, or boundary variations with no common boundaries being retained and there has been a change to dwellings or population of more than 10% of the 1996 CD. |
| |
| 7 | 2001 CD is not directly comparable because it is an amalgamation of two adjacent whole 1996 CDs to give a new 2001 CD. |
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| 8 | 2001 CD is not directly comparable due to an amalgamation of three or more adjacent whole 1996 CDs, to give a new 2001 CD. |
| |
| 9 | The 2001 CD has changed slightly when compared with the 1996 CD due to a change in the base map between censuses, for example, for Roads, Rivers or Railway lines. The 2001 CD boundary follows the same features as in 1996, but the boundary has been realigned to follow the improved base map data. Although the shape of the 2001 CD may look quite different to the 1996 CD, for statistical purposes the two are comparable. |
OTHER ASGC AREAS
Although the ABS makes annual changes to ASGC areas (excluding CDs), ASGC areas used for the 2001 Census are those as defined at 1 July 2001.
Where to locate information about changes to ASGC areas between censuses
The ASGC Manual (Statistical Geography Volume 1 - Australian Standard Geographical Classification (ASGC) (Cat. No. 1216.0)) lists changes to ASGC areas. The 2001 Edition of the ASGC Manual is applicable to the 2001 Census and provides a summary of the changes to ASGC areas from the 1996 Census to the 2001 Census.
Census Geographic Areas
In order to assist clients who require data on the basis of non-ABS administrative areas, such as Commonwealth Electoral Divisions, Suburbs and post codes, the ABS creates CD-derived boundaries as a best fit approximation for which census data may be released. These CD derived areas, known as Census Geographic Areas are designed to approximate the appropriate boundary current at the time of the 2001 Census, although in some cases they may represent an administrative boundary which came into effect shortly after the Census.
These CD-derived boundaries or Census Geographic Areas, remain effective until the next census, even though the boundary they represent may undergo changes in this period, for example an electoral redistribution may occur.
Statistical Geography Volume 2 - Census Geographic Areas Australia (Cat. No. 2905.0) contains a detailed explanation of the Census Geographic Areas and lists their codes and labels.
How to Contact the ABS
The ABS National Information and Referral Service can be contacted on any of the contacts listed below for any of the products mentioned in this fact sheet:
| Phone | 1300 135 070 |
| email | client.services@abs.gov.au |
| Fax | 1300 135 211 |
| Post | Client Services, |
| | Australian Bureau of Statistics |
| | GPO Box 796 |
| | Sydney NSW 2001 |
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