Population density in Australian city centres

Melbourne City Centre has accelerated away from Sydney's CBD in the race for inner city population density, as shown in the recently released 2011 census results. In 2001, Melbourne's density was only 5% larger than Sydney's. However the 2006 census showed that Melbourne had accelerated to achieve a density 36% larger. The city further cemented its position as Australia's most dense in 2011 in stretching its lead to 52% greater, with a population density of 14,105 persons per square kilometre.

Population density (persons/sq. km) in Australian inner cities (as defined by ABS Statistical Area Level 2)

With 33,851 individuals living in the area, the larger density of Melbourne City Centre has been achieved despite a smaller population than Sydney's 39,967. This is because it has a far smaller area, at only 2.4 square kilometre versus Sydney's 4.3 square kilometre area. These areas are demarcated by the ABS Statistical Area Level 2 boundaries, and for the purpose of illustration Sydney's is shown on a map below.

Sydney CBD (includes Sydney City, Haymarket and The Rocks), as defined by ABS Statistical Area Level 2

The only non-capital in the collection of cities, Surfers Paradise, presents some interesting results. In 2001, it had Australia's third largest population density at 5,244 persons per square kilometre. However, over the following decade, its population has declined by 1,856, causing a reduction in density. In the meantime, its neighbour 80km to the north, Brisbane, has more than doubled its CBD density to 7,188 persons per square kilometre and comfortably overtaken Surfers Paradise.

The rest of the city centres - those of Perth, Darwin, Adelaide and Hobart - have significantly lower densities in the range 1,359 to 3,112 persons per square kilometre.

Percentage of dwellings four storeys or over

The above graph illustrates the percentage of dwellings that have four storeys or more. This provides a reasonable indicator of both the population and architectural density of each city. However, the anomalous results also highlight some of the weaknesses in this indicator. The ordering aligns closely with the population density figures shown in the graph at the top. The main exception is clearly Darwin, which has a appears to have a far higher proportion of high and medium rise buildings than its lower density siblings of Adelaide and Perth.

However, Darwin's anomalous results can be explained by two factors:

1. It has the oldest population of all of the main Australian cities, with a mean age of 40 in 2011. For comparison, Melbourne's mean age is 29. It is fair to assume that older residents are likely to have less people in each dwelling, lowering density.
2. It can be hypothesised that perhaps most of Darwin's buildings go little over four storeys. This seems like a reasonable assumption given that the city clearly has a limited skyline; certainly when compared with cities such as Sydney, Melbourne, Brisbane and Surfers Paradise. 

The resurgence in city centre living has sparked intense apartment construction and gentrification processes over the past two decades. Higher-density dwellings, usually achieved through height, provide more economical projects for property developers, as long as the demand meets the supply. Increased population boosts activity in the city, particularly after office hours, and increases the perception of safety. The population-increase leads to public sector investment increases and also boosts demand for lifestyle goods and services, which leads to an endogenous feedback loop, further increasing the appeal of city living. The figures shown here demonstrate that this feedback loop is in full effect in Australia, in particular in Melbourne, Sydney and Brisbane. It is also evident in most other cities, such as Adelaide and Perth, albeit to a lesser extent.