## Comparing the residential densities of Australian cities (2011)

I’ve looked at Melbourne residential density in detail, so what about other Australian cities?  Is population weighted density a useful measure? Does population weighted density help explain differences in public transport mode shares?

For this exercise, I’ve looked at 2011 census data at the Statistical Area Level 1 (SA1) geography (currently the smallest geography for which population data is available) for Greater Capital City Statistical Areas (which include large tracts of rural hinterland). I’ve sometimes applied an arbitrary threshold of 3 persons per hectare to define urban residential areas.

### Measures of overall density

Population weighted density is a weighted average of the density of all the parcels of land in the city, with the population of each parcel of land providing the weighting. This provides a figure indicative of the residential density of the “average person”, although that’s still a little abstract. A city where a large proportion of people live in dense areas will have a much higher weighted population density than average population density.

Average density is simply the total population divided by the area of the city (or if you like, the average density weighted by the areas of each parcel of land). In calculating average residential density (which I’m doing in this post), the area would only include residential areas (I’ve arbitrarily used a threshold of SA1s with at least 3 persons per hectare).

Another measure is urban density, which considers all the land that makes up the urban city, including non-residential areas, but excluding the rural land that makes up large parts of most metropolitan areas when defined by administrative boundaries. I have not attempted to measure ‘urban’ density in this post.

Firstly here’s a table of data for the six largest Australian cities with three different measures of 2011 residential density:

 Greater Capital City Statistical Area Pop Pop (>3/ha) Area, square km (>3/ha) Pop-weighted density, persons/ ha (all SA1s) Pop-weighted density, persons/ ha (SA1s >3/ha) Average residential density, persons/ ha (SA1s >3/ha) Greater Sydney 4391578 4225278 1530 50.2 52.1 27.6 Greater Melbourne 3999924 3832366 1812 31.8 33.1 21.1 Greater Brisbane 2066134 1866794 1127 22.6 24.8 16.6 Greater Perth 1728567 1639849 963 21.6 22.7 17.0 Greater Adelaide 1225136 1161668 644 21.2 22.3 18.0 Australian Capital Territory 356563 350917 221 20.5 20.8 15.9

You’ll notice that Melbourne has a lower population than Sydney, but the total land area above 3 persons/ha is much larger.

Here are those densities in chart form:

You can see Sydney has around double the population weighted density of most other cities, but its average density is only about 60% higher. These figures show Sydney has a very different density pattern compared other Australian cities.

You can also see very little difference in weighted density whether you exclude low density land parcels or not (the blue and red bars). The density is brought down only slightly by the relatively small number of people living in very low density areas (below 3 persons/ha) within the statistical geography. Thus weighted average density is a good way to get around arguments about the boundary of the “urban” area. But then we are only measuring residential density here – and the large unoccupied spaces between residents of a city are very important when it comes to transport issues.

Can you compare population weighted density of Australian cities with international cities? Yes, but only if the parcels of land used are of a similar size and created in a similar fashion. The more fine-grained the geography (ie smaller the parcels of land), the more non-residential pockets of land will be excluded from the calculation. Anyone doing an international comparison should compare how the ABS create their geography at SA1 level with approaches of other statistical agencies. And please comment below if you get a set of comparable figures.

### Density by distance from the CBD

The differences in density can be seen a little more clearly when you look at weighted average density by distance from the city centre:

(note: I’ve chopped the vertical scale at 100 persons/ha so parts of central Sydney, Melbourne and Brisbane are off the scale).

For Perth, Adelaide, Brisbane and Canberra (ACT) you can see a weighted average density in the mid to low 20s for large areas of the city, indicating large tracts of what you might describe as traditional Australian suburbia. In Canberra this kicks in at just 2 km from the CBD, and in Adelaide it kicks in 3 km from the city.

In Melbourne the weighted average density doesn’t get below 30 until 9 kms from the CBD indicating a larger denser inner area, and in Sydney it doesn’t drop below 30 until you are 39 km from the CBD!

### Distribution of population at different densities

Here’s a frequency distribution of densities in the cities:

I’m using an interval of 1 person/ha, and the figures are rounded down to form the values on the X axis (ie: the value you see at 20 persons/ha is the proportion of the population living between 20 and 21 persons/ha).

You can see Sydney has the flattest distribution of all – indicating it has the widest range of densities of any city. Melbourne is not far behind, whereas Canberra has a lot of people living in areas between 12 and 24 persons/ha.

Note that many cities have a significant proportion of the population living at rural densities (0 to 1 person per hectare), particularly Greater Brisbane.

Another way to look at this data is a cumulative frequency distribution:

You can read off the median densities for the cities: Sydney 33, Melbourne 28, Brisbane 22, Perth 22, Adelaide 22, Canberra 19.

You can also see that 30% of people in Sydney live in densities of 44 persons/ha or more – compared to only 12% of Melburnians, 5% of Brisbanites, and less than 2% of people in the other cities.

If 15-30 persons per hectare is what you define as suburbia, then that’s 26% of Sydney, 37% of Melbourne, 44% of Brisbane, 55% of Perth, 57% of Canberra and 62% of Adelaide.

### Spatial distribution of density

For the purest view of density you cannot get past a map. The following maps show a simple density calculation at the SA1 geography.

#### Sydney

You can see vast areas of darker green (40+/ha), particularly between Sydney Harbour and Botany Bay. There are also quite a few green areas in the western suburbs, while the northern north shore has the lowest density. There are many concentrations of density around the passenger rail lines.

#### Melbourne (and Geelong)

You can see areas of dark green around the inner city, with large tracts of yellow and green in the suburbs (25-35 persons/ha). There are however areas of moderate green (30-40) in some of the newer outer growth areas to the west and north, reflecting recent planning. There’s a not a strong relationship to train lines, but this might reflect higher densities equally attracted to tram lines (not shown on the map).

Note this map is slightly different to that in a recent post where I masked out non-residential mesh blocks.

#### Brisbane

You can see dark green patches around the river/CBD, but then mostly medium to low densities in the suburbs. There’s very little evidence of higher densities in fringe growth areas. There are some denser areas around railway lines (note the map does not show Brisbane’s busway network).

#### Perth

You can see green patches around the city, but also in some fringe growth areas where new planning controls are presumably forcing up densities. There are however vast tracts of orange (15-25 persons/ha), and little evidence of higher density around the rail lines (note: a lot of the lines are freight only and the north-south passenger line has very broad station spacing and limited walking catchment as most of it is within a freeway median).

Adelaide some inner city blocks of high density, but once you get outside the green belt surrounding the city blocks, you fairly quickly head into suburban densities. There are only a few pockets of high density in the middle and outer suburbs, and very little relationship evident between density and the rail lines.

#### Canberra (and Queanbeyan)

Canberra has vast areas at low density, and only a few pockets with dark green. There are however green patches on the fringes (particularly in the far north and far south), perhaps again reflecting planning policies forcing up densities.

Sydney is really quite a different city compared to the rest of Australia, with a much larger share of the population living in high density residential areas (more than I had expected). Melbourne has a much lower population weighted density (still quite a few people living in high density areas, but much less so than Sydney), followed by four cities that aren’t that different when it comes to density: Brisbane, Perth, Adelaide and Canberra.

### What about density and public transport use?

Here’s a comparison of density (measured as both average and population weighted) and the most recent estimate of public transport mode share of motorised passenger kms for Australian cities:

Population weighted density certainly shows a stronger relationship with public transport use than average density (r-squared of 0.89 versus 0.82 on a linear regression).

If you believe that higher population density will lead to higher public transport use (for a given level of public transport service), then you would expect Sydney to be well placed to have a higher public transport mode share. Which indeed it does, but does it have the same level of public transport supply as other cities, and are all other factors equal? That’s a very difficult question to answer.

You could measure public transport service kilometres per capita, but different modes have different speeds, stopping frequencies and capacities, public transport supply will vary greatly across the city, and some cities might have more effective service network designs that others.

If all cities had the same levels of public transport supply and all other things were equal, you might expect a straight line relationship (or perhaps an exponential relationship). But Brisbane and Melbourne (and to a small extent Perth) seem to be bucking what otherwise might be a linear pattern. Are these cities doing much better with quality and quantity of public transport supply? Or is it something else about those cities?

Car ownership rates do vary between Australian cities, but this might be more a product of public transport viability for particular residents:

Also, we know that car ownership doesn’t have a strong relationship with car use.

When working population census data comes out I would like to look at the distribution of employment within cities. We know that public transport use is highest for journeys to work in the CBD (as it usually competes strongly against the car), so the proportion of a city’s jobs that are in the CBD is likely to impact the public transport mode share (at least for journeys to work). Moreover, a higher average employment density in general might be easier to serve with competitive public transport, and thus lead to a higher public transport mode share. It will hopefully also be possible to calculate weighted density of employment (at least at the SA2 level).

Finally, I’d like thank Alan Davies (The Urbanist) for inspiring this post.

### 13 Responses to Comparing the residential densities of Australian cities (2011)

1. Great post. Absolutely loved it. On your last point about measuring transport supple, perhaps you could use the value of the government subsidy for operating costs to public transport per passenger km? That strips out any increase in supply that either creates its own demand (via increased frequency and capacity) while also taking into account the benefits to public transport of higher densities.

It does have the disadvantage of depending on how well that city keeps its PT operating costs down, but otherwise could be a suitable proxy for PT supply.

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2. wombly says:

It would also be interesting to see the same maps with overlays of commuter rail lines & tram routes. There’ll be chicken and egg relationship in some areas (i.e. did the density follow rail or precede it?). However, it would highlight the parts of Australian cities that have developed high densities in their absence.

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Thanks for the suggestion. After a lot of searching the web for free data, I’ve been able to add railways to the maps (unfortunately it is not easy to only show passenger lines).

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• alan parker says:

Alan Parker .OAM

Hi Chris, a great collection of graphics.
On the melbourne which omits the less than five density rating it very clear. It would be could to have one that shows biycle access to rail as 3km dia overlap. Love to see the numbers for that my bike rail map 1992 version could with and update. Can I have your permission to use your base map to do that .
alapar@labyrinth.net .au

Last time we met In Mornington I noticed your stuff on Dutch Bike rail access.

See my Website and last paper of mine on it. I provides data on electric bike access in the Netherlands. 600,000 sold in the last 6 years mostly to elderly people.

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4. Sam says:

Great post. A major factor in Sydney’s high PT use is a high proportion of journey to work trips to the CBD and major centres being on public transport. Trying to find a link to this but one theory for this is the very high cost of private parking in Sydney’s CBD and major centres (as opposed to quality of PT).

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5. Nick says:

US and Canadian cities use Census Tracts as their main unit for statistics, which have about 5000 people each, and as a result often include lots of non residential land like parks and employment, bringing down density.

Population Weighted Density using Census Tracts has been calculated for Canadian and American urban areas, I’ve been involved in the discussion and calculations for Canada here (I’m Memph): http://www.city-data.com/forum/urban-planning/1448889-urban-density-comparisons.html#post22153272

The last page has all the weighted densities (US+Canada), plus my attempt to estimate the adjusted Australian weighted densities.

Urban Areas as defined by the US Census Bureau are basically the contiguous developed areas of a Metropolitan Area with densities of 1.93people/ha or more. They also include areas with that density in close proximity to the main urbanized area but separated by a bit of rural/low density land (the exact rules are a bit complicated). Canadian Urban Area weighted densities were calculated using the same methodology as US Urban Areas.

Do you think you could calculate the Australian weighted densities using something roughly the size of census tracts? Or alternatively using something like SA1s for Canadian/US Metro Areas (instead of urban areas), Canada has dissemination areas which are about the size of SA1s but I’m not sure how to download the data. It seems like Canadian cities are denser than Australian ones, but it’s hard to say how US cities compare to Australian ones.

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The Australian geography has SA1s at about 400 people each, and SA2s at about 10,000 people each. So unfortunately there is no established geography that averages around 5000 persons. Someone would have to manually create a new geography aggregating SA1s, which would be a lot of work. Alternatively, someone could aggregate US/Canadian census tracts to make them roughly 10,000 in size, and calculated a population weighted density using those. The second option is probably more achievable, but does anyone want to volunteer?

Sorry, I haven’t really got time to try to download Canadian dissemination areas at the moment (I have a backlog of Australian 2011 census data to analyse!).

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• Nick says:

I just aggregated them for Canadian cities by sorting them by census tract number and combining like that.

For example, Tract 1+Tract 2 = Aggregated Tract 1.5, Tract 2+3=Aggr Tract 2.5, Tract 3+4 = Aggr Tract 3.5.

This is not perfect, mostly sometimes the tracts aren’t adjacent, but a good majority of the time, they are. The new weighted densities are about the same, relative to each other as when looking at non-aggregated census tracts.

Here are the densities in inhabitants per hectare for Canadian urban areas.

Toronto 49.44
Montreal 49.37
Vancouver 42.09
Hamilton 27.53
Ottawa 26.99
Winnipeg 26.39
Calgary 25.3
Quebec 22.47
London 22.44
Edmonton 22.38
Victoria 21.81
Kitchener 20.21
Halifax 18.65

By the way, I suspect if you looked at disseminations for some Canadian cities, especially Toronto, the weighted density would jump up a lot. Much of Toronto’s density consists of small highrise clusters surrounded by single family homes (or non-residential uses in downtown areas), as well as large parklands and low density employment areas that bring down the density of many census tracts. I looked at a sample of about 50 tracts to see how the weighted density changed if you look at dissemination areas, based on that, it looks like the weighted density by dissemination area for Toronto might be around 100inh/ha.

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Nick, here are population weighted densities calculated at SA2 level for Australian cities. Sorry about the limited formatting

City, Pop weighted density SA2, Pop weighted density SA1, Ratio SA1:SA2
Canberra*, 14.8, 20.5, 1.38
Greater Brisbane, 14.2, 22.6, 1.59
Greater Melbourne, 19.9, 31.8, 1.60
Greater Perth, 13.9, 21.6, 1.55
Greater Sydney, 28.1, 50.2, 1.79

*Canberra = Australian Capital Territory.

The SA2 based weighted densities are much lower (as you would expect), and the ratio between the SA1 and SA2 weighted population densities range between 1.38 and 1.79, which is a fair amount. However Sydney is still the densest, followed by Melbourne, then Perth, Brisbane, Adelaide and Canberra are still much the same. How big are the Canadian dissemination areas?

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7. Nick says:

Dissemination Areas typically have 400-700 people according to StatsCan. Also when I aggregated the census tracts, they turned out to be more around 9000 people (so 4500 per CT), but I think this should still be relatively comparable to Australian cities.

The main thing that might have to be tweaked is the way the regions as a whole are defined. The Canadian urban areas don’t include areas significantly separated from the urban area by rural land, so for example, Geelong wouldn’t be considered part of Melbourne’s urban area. I did however include census tracts with rural (<193ppl/km2) densities if the census tract contained denser areas near the main urban area. Census tracts with no population or low densities surrounded by denser census tracts, like industrial areas or large parks were also included.

There's also a few tricky cases where the land between two separate metropolitan areas might be urbanized, so they could be considered a single urban area, but are separated because they are separate metro areas. In Canada, you see this with Toronto, Oshawa and Hamilton. This is also common in the United States, with San Jose and San Francisco; Los Angeles and Riverside-San Bernardino; Washington and Baltimore and New York and Philadelphia.

The weighted density for many Canadian cities would probably drop by about 10% if I include the whole metropolitan area and not just the urban area. That would take a while, but I can do that, especially since it would also allow me to compare to US cities, since 2010 data is only available for metro areas, for urban areas, the US Census Bureau currently only has 2000 data.

The US only seems to have census block groups between census tracts and census blocks (city blocks), which are a bit too big at about 1500 people each.

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8. Nick says:

Here are the weighted densities for aggregated census tracts, same as above, but for metropolitan areas instead of urban areas.

Toronto 46.41
Montreal 44.8
Vancouver 40.52
Hamilton 26.27
Winnipeg 24.17
Calgary 23.79
Ottawa 22.64
Quebec 20.64
Victoria 19.86
Kitchener 19.68
London 18.86
Edmonton 18.5
Halifax 15.97

Some cities had relatively significant decreases when comparing metropolitan areas to urban areas, either because they included a lot of rural or very low density exurban areas (Ottawa, Halifax), or a lot of commuter towns (London, Edmonton, Montreal, Toronto).

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9. David says:

It would be interesting to see the geographic distribution of Employment density (workplaces). To some approximation, the difference between Residential locations and Employment locations would be indicative of the demand for transport.

In the case of Adelaide where I live, the public transport system is CBD-centric radial, but I suspect that CBD-based employment is now a minority. Understanding of the distance and direction that people commute would be very helpful in transport planning.

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10. […] Loader at Charting Transport looked into this further for cities from various countries, then in more detail on Australian cities, and finally into great detail on just Sydney. Two maps looking at employment density and public […]

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