Changes from the previous edition of the ASGS

Overall, the Main Structure and Greater Capital City Statistical Areas (GCCSA) provide high stability and good statistical comparability to ASGS Edition 3 (2021). Changes to Mesh Blocks, Statistical Areas Level 1 (SA1) and Statistical Areas Level 2 (SA2) mainly reflect population growth, largely on the edge of urban areas. There are some minor changes to Statistical Areas Level 3 (SA3) mainly to reflect population growth. In this edition, there are no major changes to Statistical Areas Level 4 (SA4) or GCCSAs.

The ABS provides several resources to explain changes to boundaries and codes, and to help manage the transformation of data across different ASGS editions and other geographies. More information about changes for this edition is included below. Information about converting data between ASGS Edition 3 and 4 is included in Using the ASGS.

When analysing population data, ASGS Edition 4 can be compared to previous editions of the ASGS for time series. There may be some cases, for example when using environmental data, where alignment changes will need to be considered.

Changes to Mesh Blocks, SA1s, SA2s and SA3s are made primarily through splitting areas to reflect changes, such as new housing developments or altered transport infrastructure. These changes account for recent population growth and enable access to meaningful statistics on communities of interest.

The resulting net increase in numbers of Mesh Blocks, SA1s, SA2s and SA3s is shown below.

The design of new Mesh Blocks, SA1s, SA2s and SA3s has resulted in small net increase percentages for each geography (1.8%, 2.7%, 4.0%, and 2.2% respectively). This reflects the small amount of change introduced in ASGS Edition 4 design to address population growth and change since the last edition.

The high percentage of unchanged Mesh Blocks, SA1s, SA2s and SA3s in Edition 4 shows the overall stability of the ASGS.

The only changes to the boundaries for SA4s and GCCSAs are minor alignment changes.

Boundary changes have occurred in locations where the design criteria are no longer being met.

The following principles apply to Main Structure and GCCSA design:

• Where possible, changes are accommodated by simple splits of existing boundaries.
• Where a simple split is not possible, two or more boundaries are merged, and the merged area is redesigned from the next level down in the hierarchy.
• Boundaries are designed to remain stable where possible.
• Minor boundary alignment changes are made to maintain alignment to source data for physical infrastructure and physical geography.

Most of the change in ASGS Edition 4 is the result of simple splits. The following images show an example of one large Mesh Block in 2021 that is split into 28 smaller Mesh Blocks in 2026. This is typical for growth areas on the edge of large cities.

The following images show a similar design process where a large SA2 has been split into 3 smaller SA2s due to high growth.

Merges were minimised in ASGS Edition 4. Where necessary, boundaries were merged to avoid splitting existing infrastructure or a new growth area. Images below show an example of two Mesh Blocks that have been merged to ensure several dwellings can be address coded more accurately.

In some circumstances, simple splits and merges are not enough to account for growth and change. Where ASGS Edition 3 boundaries had to be both merged and split, these boundaries are considered ‘redesigned’. This typically occurs in high growth areas where previous land use has been replaced by new development.

Images below show an example of SA1 redesign in the South Ripley - Deebing Heights SA2. The 2021 SA1 boundary followed an old suburb boundary which has since been revised to accommodate new housing developments. The original SA1s were merged and then split into new SA1s. Redesigning boundaries in this way has minimal effect on the comparability of data over time as, in previous editions of the ASGS, growth areas generally contained little or no population.

Alignment refers to small area changes that are expected to have minimal or no change to population statistics. This type of change will be evident in area based correspondences between ASGS Edition 4 and other ASGS editions but will not affect population weighted correspondences. Unlike other boundary changes, alignment does not result in a code change unless significant change has occurred. When significant alignment occurs, the Mesh Block is retired and a new code allocated.

For ASGS Edition 4, there has been minor alignment change along the coastline. The images below show where alignment has occurred between Edition 3 and Edition 4.

Boundary codes and names change when an area is split, merged, or redesigned.

Code changes also occur when a boundary change in a higher level geography is made, affecting all lower level geographies which aggregate to form the higher level boundary. This is due to the hierarchical coding system of the ASGS. The only exception is Mesh Blocks as the building block geography of the ASGS.

Alignment changes do not result in code or name changes at any level unless significant change has occurred.

For more information on the ASGS code changes, please refer to the tables below in the List of changes section.

The ABS provides several resources to help understand changes to boundaries, codes and labels to help manage the transformation of data across different ASGS editions and other geographies. These resources include ABS Maps, various correspondences and the List of changes section.

Change flags are included on all Main Structure and GCCSA boundaries as an attribute. This attribute indicates whether an area has changed since ASGS Edition 3 and what the nature of that change is.

ASGS Edition 4 has updated the label names to match the Australian Government Style Manual for geographies where the state abbreviation of Victoria and Tasmania has been used in an ASGS name i.e. updating ‘Vic.’ and ‘Tas.’ to ‘Vic’ and ‘Tas’ respectively. These changes have been reflected in a Change Flag ‘3’ and Change Label ‘Name change’ across all geographies within ASGS Edition 4.