Musing on city definitions: Australia

I spent a few summer weeks at CASA, UCL, who very kindly hosted me. There was a lot of interesting discussion on “how to define cities”, and how statistical observations, inferences, analyses, and results could change or vary as the underlying city definitions are varied. At the recent symposium on Cities as Complex Systems, in Hannover, Germany, (where I presented some of our inequality results), this was also recurring topic of discussion. So, back to Sydney, I was thinking about how we define “cities” or “urban areas” in Australia.

So, back to Sydney, I was thinking about how we define “cities” or “urban areas” in Australia, and whether alternative definitions are possible or feasible, and whether our statistical and geographic analysis should be performed at various city definition levels before any conclusions are finalized. For example, here is an example of such analysis for the UK.

The Australian Bureau of Statistics (ABS) defines the statistical geography of Australia at four levels: Statistical Areas Levels 1 (smallest), 2, 3, and 4 (largest), each higher level built on aggregations of the level lower, and each based on rough criteria of social and economic connectedness and population cut-offs. At each level, these cover the whole of Australia, without gaps or overlaps. The detailed description is available here. Significant Urban Areas (SUAs) are then defined by “concentrations of urban development with populations of 10,000 people or more using whole Statistical Areas Level 2 (SA2s). They do not necessarily represent a single Urban Centre, as they can represent a cluster of related Urban Centres with a core urban population over 10,000. They can also include related peri-urban and satellite development and the area into which the urban development is likely to expand”. Here is an interactive map with the SUA boundaries and their  2011 Census populations, for the whole of Australia.

The above definition seems reasonable enough, and at least, is a functional definition (as opposed to an administrative definition [e.g. suburbs, Local Government Areas (LGAs)]. However, even with this definition, the answer to “what is a city or a connected urban system/entity” may not be obvious. For example, here is Tasmania with its SUAs, where it is easy to see that each SUA is reasonably well-defined. (The colours represent the 2011 Census populations of each SUA).

TAS

On the other hand, here is New South Wales and the area around Sydney. Given the near continuous spreading “band” around Sydney, the definition of a “city”, “city boundaries”, or “city limits” now becomes harder, both from the size (population and density) perspective, as well as the socio-economic connectedness perspective. For example, do we consider Wollongong (just south of Sydney) as part of the same urban system (with Sydney), or a separate urban system?

SYD

Similarly, here is Victoria and the area around Melbourne, and one can see a similar type of SUA distribution, with strong spatial dependence between SUAs around Melbourne.

MEL

This geographical question is an important one for economic and planning analysis and also has important policy implications. Considering a regional/national perspective, what is a “city”? To further complicate matters, functional or statistically derived definitions often do not correspond with administrative-historical divisions and while the socio-economic processes are better understood (or at least with more scientific integrity) with functional definitions, political and policy decision making often happens at the administrative-historical level of definitions. With the differing geography of these two definitions, how should a scientific understanding at the functional level be enacted into socio-political decision-making at the administrative level?