What does the census tell us about motor vehicle ownership in Australian cities? (2006-2016)

Sun 30 July, 2017

With the latest release of census data it’s possible to take a detailed look at motor vehicle ownership in Australian cities.  This post will look at ownership rates across time and space, and compare trends between car ownership, population growth, and population density. And this time I will cover 16 large Australian cities (but with a more detailed look at Melbourne).

I’ve measured motor vehicle ownership as motor vehicles per 100 persons in private occupied dwellings. If you want the boring but important details about how I’ve analysed the data, see the appendix at the end of this post.

I’ve used Tableau Public for this post, so all the charts and maps can be explored, and they cover all sixteen cities.

Is motor vehicle ownership increasing in all cities?

Elsewhere on this blog I’ve shown that motor vehicle ownership is increasing in all Australian states, but what about the cities? Here are the overall results for Australia’s larger cities, on motor vehicles per 100 persons basis. Note that the Y-axis only goes from 54 to 70, so the rate of change looks steeper than it really is.

(you can explore this data in Tableau)

Sydney unsurprisingly has the lowest average motor vehicle ownership, followed by Melbourne, Brisbane (Australia’s third biggest city), and then Cairns and Darwin. Perth was well on top, with Sunshine Coach rapidly increasing to claim second place. Most of the rest were around 66-68 motor vehicles per 100 persons in 2016.

But Melbourne is showing a very different trend to most other cities, with hardly any increase in ownership rate across the ten years (also, Canberra-Queanbeyan saw very little growth between 2011 and 2016).

At first I wondered whether Melbourne was a data error. However, I did the one data extract for all cities for both population and motor vehicle responses, and I’ve also checked for any potential duplicate SA1s. So I’m confident something very different is happening in Melbourne.

So let’s have a look at Melbourne in more spatial detail, starting with maximum detail over time:

(you can zoom in and explore this data in Tableau).

You can see lower ownership in the inner city, inner north, inner west, and the more socio-economically disadvantaged suburbs in the north and south-east. You can also see lower motor vehicle ownership around train lines in many middle suburbs. Other pockets of low motor vehicle ownership are in Clayton (presumably associated with university students) and Box Hill, and curiously some of the growth areas in the west and north. Very high motor vehicle ownership can be seen in wealthier areas and the outer east.

It’s a bit hard to see the trends with such a detailed map, so here’s a view aggregated at SA2 level (SA2s are roughly suburb-sized).

No doubt you are probably distracted by the changes in the legend. That’s because in 2006 there were no SA2s in the <20 and 30-40 ranges at all, and the 30-40 range is only present in 2016. That is, the legend has to expand over time to take into account SA2s with lower motor vehicle ownership rates.

You’ll notice a lot more light blue and green SA2s around the city centre, plus Clayton in the middle south-east switches to green in 2016.

Looking at it spatially, more areas appear to have increasing rather than decreasing motor vehicle ownership. But not all SA2s have the same population – or more particularly – the same population growth. So we need to look at the data in a non-spatial way.

Here’s a plot of population and motor vehicle ownership for all Melbourne SA2s, with the thin end of each “worm” being 2006 and the thick end being 2016.

Okay yes that does looks like a lot of scribbles (and you can explore the data in Tableau to find out what is what), but take a look at the patterns. There are lots of short worms heading to the right – these have very little population growth but some growth in motor vehicle ownership. Then there are lots of long worms that are heading up and to the left – which means large population growth and mostly declining motor vehicle ownership.

Here’s a similar view, but with a Y-axis of change in population since 2006:

(explore in Tableau)

The worms heading up and to the left include both inner city areas and outer growth areas. These areas seem to balance out the rest of Melbourne resulting in a stable ownership rate overall.

Some SA2s that are moving up and to the right more than others include Sunbury – South, Langwarrin, and Mount Martha. And there are a few in population decline like Endeavour Hills – South, Mill Park – South, and Keilor Downs.

The inner city results are not surprising, but declining ownership in outer growth areas is a little more surprising.

Is this to do with growth areas being popular with young families, and therefore containing proportionately more children?

Here’s a map of the percent of the population in each CD/SA1 that is aged 18-84 (ie approximately of “driving age”):

(view in Tableau)

The rates are highest in the central city and lowest in urban growth areas. And if you watch the animation closely, you’ll see areas that were “fringe growth” in 2006 have since had increasing portions of population aged 18-84, presumably as the children of the first residents have reached driving age (and/or moved out).

So what is happening with motor vehicles per 100 persons aged 18-84? Is there high motor vehicle ownership amongst driving aged people in growth areas?

Yes, a lot of growth areas are in the 80-85 range, similar to many middle suburban areas (view in Tableau)

Here’s the same thing but aggregated to SA2 level (explore in Tableau):

Motor vehicle ownership rates in most growth areas are similar to many established middle suburbs, but lower than non-growth fringe areas which show “saturated” levels of ownership (where there is roughly a one motor vehicle per person aged 18-84), particularly the outer east.

However in the outer growth areas of Sunbury (north-west) and Doreen (north-north-east), ownership rates are close to saturation in 2016.

But is the rate of motor vehicle ownership still declining amongst persons aged 18-84 in the outer growth areas? Here’s a similar chart to the previous one, but with ownership by persons aged 18-84 (explore in Tableau):

You can see most of the outer growth areas still have declining ownership rates. You can also see some established suburbs with strong population growth and increased ownership, including Dandenong and Braybrook (which includes the rapidly densifying suburbs of Maidstone and Maribyrnong).

Here’s a spatial view of the changes in ownership rates (area shading), as well as total changes in the household motor vehicle fleet (dots ). (I’ve assumed non-reporting private dwellings have the same average motor vehicle ownership as reporting dwellings in each area).

(explore in Tableau)

You can see outer growth areas shaded green (declining ownership), but also with large dots (large fleet growth).

But also you can see some declines in ownership in the middle eastern and north-eastern suburbs, and some non-growth outer suburbs, which is quite surprising. I’m not quite sure what might explain that.

You’ll also notice the scale for the dots starts at -830, which accommodates Wheelers Hill (in the middle south-east) where there has been a 2% decline in population, and 6% decline in motor vehicle fleet.

Okay, so that’s Melbourne, what about ownership rates amongst “driving aged” people in other cities?

Trends in motor vehicles per persons aged 18-84

(explore in Tableau)

The trends are similar, but Melbourne is even more interesting on this measure. It has declined from 81.3 to 80.7, bucking the trend of all other cities (although Canberra only grew from 88.4 in 2011 to 88.5 in 2016).

How does motor vehicle ownership relate to density?

Here’s a chart showing population weighted density and motor vehicle ownership for persons aged 18-84 for SA2s across all the big cities in 2016 (explore in Tableau):

Some dots (central Melbourne and Sydney) are off the chart so you can see patterns in the rest. I’ve labelled some of the outliers. The general pattern shows higher density areas generally having lower motor vehicle ownership.

Is densification related to lower motor vehicle ownership?

Here’s a chart showing how each city has moved in terms of population-weighted density (measured at CD or SA1 level) and ownership for persons aged 18-84, with the thick end of each worm 2016, and the thin end 2006.

(Note that the 2006 population weighted density figures are not perfectly comparable with 2011 and 2016 because they are measured at CD level rather than SA1 level, and CDs are slightly larger on average than SA1s)

(explore in Tableau)

You can see Sydney is a completely different city on these measures, and also that Melbourne is the only city heading to the left of the chart. Canberra is also bucking the trend between 2011 and 2016.

We can look at this within cities too. Here’s all the Local Government Areas (LGAs) for all the cities (note: City of Sydney and City of Melbourne are off the top-left of the chart)

(explore in Tableau)

Many Melbourne and Sydney LGAs are rising sharply with mostly declining motor vehicle ownership. But then there are Sydney LGAs like Woollahra, Mosman and Northern Beaches in Sydney that are showing increasing motor vehicle ownership while they densify (probably not great for traffic congestion!).

And we can then look inside cities. Here is Melbourne (again, several inner city SA2s are off the chart):

Some interesting outliers include:

  • The relatively dense Port Melbourne, Albert Park, Elwood with relatively high motor vehicle ownership.
  • The land-locked suburb of Gowanbrae with medium density but rapidly increasing car ownership (which has a limited Monday to Saturday bus service).
  • The growth area of Cranbourne South with reasonable density but more than saturated car ownership.
  • Relatively medium dense but low motor vehicle ownership of Clayton and Footscray.

Explore your own city in Tableau. You know you want to.

What are the spatial patterns of motor vehicle ownership in other cities?

The detail above has focussed on Melbourne, so here are some maps for others cities. You can explore any of the cities by zooming in from this Tableau map (be warned: it may take some time to load as I’ve ignored Tableau’s recommendations about how many showing more than 10,000 data points!). In fact for any of the maps you’ve seen on this blog, you can pan and zoom to see other cities.

To help see the changes in motor vehicle ownership between censuses more easily, I’ve prepared the following detailed animations.

Sydney

 

Brisbane

 

Adelaide

Perth

(Find Mandurah in Tableau)

Canberra

Hobart

Darwin

Cairns

Townsville

Sunshine Coast

Geelong

Central Coast (NSW)

Newcastle – Maitland

This post has only looked at spatial trends and the relationship with population density. There’s plenty more to explore about car ownership with census data, which I aim to cover in future posts.

I hope you’ve enjoyed this post, and found the interactive data at least half as fascinating as I have.

Oh, and sorry about some of the maps showing defunct train lines. I’m using what I can get from the WMS feed from Geoscience Australia.

Appendix – About the data

The Australian census includes the following question about how many registered motor vehicles were present at each occupied private dwelling on census night. This excludes motorcycles but includes some vehicles other than cars (probably mostly light vehicles).

96% of people counted in the 2016 census were in a private dwelling on census night, and 93.6% of occupied dwellings filled in the census and gave an answer to the motor vehicle question. So the data can give a very detailed – and hopefully quite accurate – picture.

I’ve used two measures of motor vehicle ownership:

  • Motor vehicles per 100 population (often referred to as “motorisation” in Europe), and
  • Motor vehicles per 100 persons aged 18-84

The first is easy to measure and easily comparable with other jurisdictions, but the second gives a better feel for what proportion of the “driving aged” population own a car. In an area with good alternatives to private transport, you might expect lower ownership rates.

Setting the lower age threshold at 18 works well for Victoria (imperfectly for other states with a lower licensing age), and 84 is an arbitrary threshold during the general decline in drivers license ownership by older people. So it’s not perfect, but is indicative, and certainly takes most children out of the equation.

As the motor vehicle question is based on what was parked at the dwelling on census night, I’ve used population present on census night (place of enumeration). That works well if someone was absent on census night and took their car with them, but not so well if they were absent and left their car behind (e.g. they took a taxi to the airport). You cannot win with that, but the census is timed in August during school and university term to try to minimise absences.

When calculating ownership rates, I’ve excluded people in dwellings that did not answer the motor vehicle question, and people in non-private dwellings. This is more robust than assumptions I made in previous posts on this topic so results will vary a little.

For 2011 and 2016, the census data provides counts of the number of dwellings with 0, 1, 2, 3, .. , 29 motor vehicles, and then bundles the rest as “30 of more”. For want of a better assumption, I’ve assumed dwellings with 30 or more motor vehicles have an average of 31 motor vehicles, which is probably conservative. But these are so rare they shouldn’t make any noticeable difference on the overall results.

As shorthand, I’ve referred to “motor vehicle ownership” rates, but you’ll note the census question includes company vehicles kept at home, so it’s not a perfect term to use, but then company vehicles are often available for general use.

I’ve used the 2011 boundaries of Significant Urban Areas (SUA) for each city, which are made up of SA2s and leave a good amount of room for urban fringe growth in 2016. However they do exclude some satellite towns (such as Melton, west of Melbourne).

I’ve extracted data at SA1 level geography for 2011 and 2016, and Collector District (CD) geography for 2006. In urban areas, SA1s average around 400 people while the older Collector Districts of 2006 averaged around 550 people. These are the smallest geographies for which motor vehicle and age data is available in each census. ABS do introduce some small data randomisation to protect privacy so there will be a little error well summing up lots of parcels.

I’ve generally excluded parcels with less than 5 people per hectare as an (arbitrary) threshold for “urban” residential areas. I’ve mapped all parcels to the 2016 boundaries of Local Government Areas and SA2s, and the 2011 boundaries of SUAs (2016 boundaries have not yet been released). Where boundaries do not line up perfectly, I’ve included a parcel in an SAU, LGA, or SA2 if more than 51% of the parcel’s area is within that boundary. The mapping isn’t perfect in all cases, particularly for growth area SA2s and 2006 CDs. See the alignments for SA2s, LGAs in Tableau.

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How is Melbourne’s population density changing? (2006-2016)

Sun 9 July, 2017

With the first major release of 2016 census data, it’s possible to take a detailed look at the latest population density numbers in Melbourne. This post will explore how and where Melbourne’s density is increasing by comparing data from the 2006, 2011, and 2016 censuses.

About the data

This post looks at data mostly at the mesh block level. Mesh blocks are the smallest geographic unit at which the ABS publishes population and dwelling counts. They aim for each mesh block to have the same land use, and between 30 and 60 dwellings (where residential).

I’ve used Tableau Public to create this post, so you will be able to explore the maps in more detail yourself, using the links in this post. Be warned though: Tableau tried to dissuade me several times from adding so many mesh blocks to the maps and charts, so they may take a little time to load and update.

Background map data has been used that is copyright © The State of Victoria, Department of Environment, Land, Water & Planning 2017

What does Melbourne’s population density look like?

Firstly, here’s the population density picture for most of Melbourne (you will probably need to open this is in a new window to see it more clearly).

(explore in Tableau)

Here is a closer look at Melbourne’s growing west, stretching as far as Bacchus Marsh:

You can see the expanding urban area, and you might also notice some of the new areas are coming up in red (densities in the 60-70s). This demonstrates that recent urban growth areas are much more dense than growth areas of 5-10 years ago. However that’s not happening in growth areas of Bacchus Marsh (which is outside Melbourne’s Urban Growth Boundary.

Here is a closer look at the northern growth areas:

You can see large areas of orange and red in north-western Craigieburn (top left of map) and Roxburgh Park in 2016 – that’s around 50-60 people per hectare, around double that of old-school suburbia.

Here’s the south-east growth corridors, where new high density areas are less widespread:

There’s also been plenty of change in population density in the inner city:

If you look carefully you can see a lot more purple around the city centre, but also plenty of population density increase around Brunswick in the north and Footscray in the west.

So this is this increase in population density due to rising dwelling densities or more people per dwelling?

Here is the dwelling density around Craigieburn:

(explore in Tableau)

There are dwelling densities of over 20 per hectare in the new north-western areas, which is likely to be contributing to higher population density.

Here’s a map showing the average dwelling occupancy – the ratio of population to dwelling counts. Note: this includes unoccupied dwellings at census time, so it’s not the average occupancy of occupied dwellings.

(explore in Tableau)

One clear trend is that the growth areas have higher average dwelling occupancy, quite probably related to young families moving into those areas. This, together with smaller block sizes, is likely leading to higher population density in growth areas.

If you look carefully you’ll also see some older outer areas with reducing average dwelling occupancy – quite possibly family homes where children have moved out.

What are the broader trends in density?

The above maps are incredibly detailed, and you are probably struggling a little with so many blocks of different colours. Time to take a step back.

Calculating the straight population density of Greater Melbourne makes no sense because most of the land within the statistical boundary is non-urban.

In other posts I’ve looked at population-weighted density, which is the average population density of all areas, weighted by the population of each area. It aims to summarise the population density at which the “average” person lives, which takes out the impact of large areas that are sparsely populated. But it is important to keep in mind that “average” does not mean typical (I’ll come back to that).

Here’s a chart showing Melbourne’s populated weighted density, as well as average density for mesh blocks with a population density of at least 5 persons/ha (an arbitrary threshold for urban residential areas).

Yes, that’s a massive increase in population-weighted density. So what’s going on here?

Well, here’s a chart showing the densities at which people in Melbourne lived at each census:

If you look at the green levels and below, you’ll notice in all years less than 2.5 million people lived at densities of below 35 persons/ha. There’s been little population growth at such lower densities – it’s mostly been at 35 persons/ha and above, pushing up the population-weighted density.

Greater Melbourne’s population-weighted density of 59 is quite high relative to the density distribution within Melbourne. Only around 600,000 people live at this or higher densities, with around 4 million living at lower densities. That’s a classic problem with summary statistics.

Where is the population-weighted density increasing the most? Here’s a map showing population-weighted densities by SA2 (2016 boundaries):

(explore in Tableau)

There are big increases in population weighted densities across inner Melbourne, but also in places like Clayton, Box Hill, Preston East, Doncaster.

What’s going on there? Box Hill’s population-weighted density went from 45 in 2011 to 72 in 2016. Here’s a look at the mesh block density for the area:

You can see a little densification outside the main centre on the rail line, but if you look really carefully, you’ll see some tiny purple mesh blocks right in the centre – apartment towers with large populations are bringing up the populated weighted density of the whole SA2.

What about median densities?

While no one statistic will tell you about “typical” density, we can calculate median density, which tells you the density in which the middle person lives.

Greater Melbourne’s median population density hasn’t increased a great deal:

Here’s a look at median density by SA2 (open in a new window to see more detail, including the numbers):

(explore in Tableau)

(note that a different set of colour ranges used to the previous maps because the medians are so close)

You can see a lot more red on the map – i.e. more and more areas of Melbourne have a median population density of in the 40s.

How has population and density changed by distance from the CBD?

Firstly, here’s a reference map of distances from the CBD:

(explore in Tableau)

Here’s the population of Melbourne by density and distance from the CBD:

(explore in Tableau)

You can see a lot of growth close to the CBD, but also around 20-23 km from the CBD, which includes several outer suburban growth areas.

Here’s a look at five year population growth by distance from the CBD:

In the five years to 2016 there was a lot more growth within 30 kms of the CBD, particularly within 5 km.

Finally, which mesh block densities are becoming more common. Here is the five year change in population by (mesh block) population density:

In the five years to 2011, the biggest population increase was at densities of 30 to 45 persons/ha. In the five years to 2016, the biggest population growth was at densities of 35 to 55 persons/ha. There was also considerable growth at densities of more than 400 persons/ha, which is likely to reflect new apartment towers.

You’ll find a few other charts in Tableau. Hope you enjoyed this post.


Are Melbourne’s suburbs full of quarter acre blocks?

Sun 22 May, 2016

A lot has been said about the great Australian dream of moving to the suburbs and living on a quarter acre block. But is Melbourne suburbia actually full of quarter acre blocks? Where are they to be found? Are they disappearing? This post delves into block sizes in Melbourne.

Where are the quarter acre blocks?

A quarter-acre translates to 1011.7 square metres in modern units, but for the purposes of this post I’ll allow some leeway and count any block between 900 and 1100 square metres. For this post I’ve also filtered out blocks in planning zones that cannot include dwellings (eg industrial areas), but that does mean I’ve included blocks in mixed use zones, commercial zones, etc. So not every block counted is residential. Also some larger blocks might contain multiple small dwellings but not actually be subdivided (eg a block of flats).

First up, here is a map of Melbourne showing the prevalence of quarter acre blocks. It looks like there are lots of them, but because the blocks are so small, the total area occupied by quarter-acre blocks is significantly over-represented on this large scale map.

Melbourne quarter acre block map

There are larger concentrations in the outer north-east and outer-east, but very few blocks in the current growth areas to the west, north and south-east.

Here are the top 20 suburbs for numbers of quarter-acre blocks:

Mooroolbark 1625
Rye 1545
Ferntree Gully 1504
Boronia 1471
Croydon 1437
Mount Martha 1430
Eltham 1229
Mount Eliza 1125
Werribee 1054
Sunbury 1035
Lilydale 996
Mornington 982
Reservoir 978
Balwyn North 936
Berwick 898
Upwey 897
Pakenham 772
Langwarrin 767
Kilsyth 732
Greensborough 724

There are almost 78,000 quarter-acre blocks within Melbourne’s Urban Growth Boundary, which sounds like a lot, but is only 3.75% of the 1.8 million blocks in my dataset.

So what are typical block sizes in Melbourne?

For this analysis I’m considering blocks within land use zones that can include dwellings, that are also within the urban growth boundary. But I’ve excluded blocks of less than 40 square metres on the assumption these are unlikely to contain dwellings.

Here’s the frequency distribution of block sizes in Melbourne:

The most common block size is 640-660 square metres, and 34.5% of blocks are between 520 and 740 square metres. The median is 540-560 square metres. 180-200 is the most common smaller block size, and there is a small spike in block sizes of 1000-1020 square metres, which includes the quarter-acre block. But quarter-acre blocks are certainly very uncommon.

I’ve calculated the median block sizes for all suburbs within Melbourne’s Urban Growth Boundary.

The inner city has median block sizes under 300 square metres, and 300-500 is typical in the inner northern and western suburbs. Block sizes are larger in the middle and outer eastern suburbs, older suburbs in the south-east, and blocks along the Mornington Peninsula. But the more recent growth areas to the west, north and south-east see median block sizes of between 400 and 500 square metres (purple), reflecting higher dwelling densities encouraged by current planning policy for growth areas. Quarter-acre blocks are the median only in places like Upwey, Belgrave and Portsea.

Inner city Carlton has the lowest median of 100-120 square metres, followed by Cremorne, North Melbourne, South Melbourne at 120-140 square metres, and then Abbotsford, Fitzroy North, Port Melbourne, Richmond, West Melbourne at 140-160 square metres. Urbanised suburbs at the other end of the scale include Park Orchards at 3020, Selby at 1440, and Warrandyte at 1260.

There are two interesting outliers in the central city: Southbank (in yellow) has a median block size of 980 square metres, and Docklands (in blue) has a median of 660 square metres. Both have been redeveloped in recent decades with many medium to high-rise apartment towers on those larger blocks.

Beyond these medians, there is a lot of variation within suburbs. Let’s go for a wander around the city.

Mooroolbark has the highest count of quarter-acre blocks and a median size of 840 square metres. As well as larger blocks, you can see a lot of further subdivision, particularly close to the train line (thin black line).

You may have noticed in the suburb map above a black coloured suburb in the middle south-eastern suburbs. That suburb is Clayton, and here is how it looks:

While blocks of 700-800 square metres were probably typical in the original subdivision, further subdivided blocks now outnumber the larger blocks, with a median of 260 square metres. Clayton of course is home to a major Monash University campus, and I suspect a lot of the smaller blocks house students.

A bit further down the line in Noble Park you can see extensive further subdivision near the rail line, surrounded by almost uniform blocks of 500-600 square metres:

Heading further south, Cranbourne is an interesting mix. The inner core (old town) has larger blocks but lots of further subdivision. This is surrounded by many blocks of around 700-800 square metres, but the most recent development has much smaller bocks, most less than 500. It’s a bit like tree rings, with each ring of incremental urban growth reflecting the preferred new block size of the time.

The area around Berwick also has a wide variety of block sizes, depending on the timing of development:

Here is the Frankston area:

Again significant further subdivision in central Frankston, a variety of block sizes in different parts of Langwarrin, and lots of large blocks in Frankston South and Mount Eliza (in some of the pink areas most blocks are over 2500 square metres).

In the middle northern suburbs you can see suburbs from an era when new block sizes were relatively large, and they’ve since had extensive subdivision. Here is Pascoe Vale:

Here is Reservoir. You can see smaller blocks in the surrounding suburbs:

The large block area to the west of the train line was apparently developed around the 1960s.

And to the west St Albans is another suburb with larger blocks being subdivided:

And further east there is a lot of further subdivision in Boronia and Bayswater, particularly near the rail stations:

The north-west corner of Templestowe has not too many larger blocks yet to be subdivided. But to the south-east you can see areas with blocks larger than 1200 square metres (light pink).

The area around Eltham has many large blocks, including many larger than quarter-acres. There has been quite a bit of subdivision around the rail stations however.

Another area with many large blocks is around Upwey/Belgrave:

A significant proportion of blocks are larger than a quarter-acre, with a median of 1060 in Belgrave, 1120 in Upwey, 1000 in Tecoma, and 980 in Upper Ferntree Gully.

If you want a quarter-acre block relatively close to the city, then Balwyn North has quite a few (many with swimming pools). Good luck saving a deposit for those.

But if a quarter-acre block isn’t big enough and you can afford the real estate, then you might want to try Canterbury or Deepdene, also relatively close to the city:

Or of course Toorak with plenty of very large blocks even closer to the city (although many will contain apartment buildings).

Essendon also has some larger blocks, including some quarter-acres:

There has been plenty of further subdivision, but there is also a stripe of green that is mostly in tact (a restrictive covenant applied perhaps?). You can also see the recent Valley Lake development in purple in Niddrie.

Most of the growth areas have small blocks, but here are some exceptions in eastern Doreen:

So there is plenty of variation in block sizes across Melbourne, but not that many quarter-acre blocks. Perhaps we should talk more about the one-seventh-acre block.

Data acknowledgement

This analysis was made possible with data available from data.vic.gov.au under a creative commons license. The data is Copyright © The State of Victoria, Department of Environment, Land, Water & Planning 2016.

I have used November 2015 property boundary data and May 2016 planning zones (sorry, not quite aligned, but this post has been a while in the making and the differences are unlikely to be significant).


How do Australian and European cities compare for population and area?

Sun 6 December, 2015

Following on from my previous post comparing the density of Australian and European cities, there has been some interest in the relative size of Australian and European cities. This post takes a quick look.

To make comparisons, I’ve taken the square kilometre population grid data for Europe and Australia, and summed the population and number of cells within the urban area/centre boundaries (as discussed in last post) that have at least 100 residents (ie 1 person per hectare or more) for each city. I’ve included this (arbitrary) threshold as some urban area boundaries seem to include some non-urban land. It means that I’m approximately measuring the populated areas of cities, and large parks, industrial areas, airports, etc may therefore be excluded in this analysis.

Here’s a chart of population versus populated area (click to enlarge):

 

So Melbourne is about the same size as London and Paris but has less than half the population. Brisbane is a similar size to Milan, with half the population. Perth is larger than Berlin, but has around half the population. Adelaide has a similar population to Seville and Sofia, which are about a third the size. Sydney has a similar population as Barcelona but is almost four times larger.

Because I couldn’t label all the cities in the chart above, here is a data table (smaller values in red, larger values in blue):

AU EU city data table
I’m hoping to add Canadian and US cities to my analysis soon.


Comparing the densities of Australian, European, Canadian, and New Zealand cities

Thu 26 November, 2015

[updated March 2016 to add Canadian and New Zealand cities]

Just how much denser are European cities compared to Australian cities? What about Canadian and New Zealand cities? And does Australian style suburbia exist in European cities?

This post calculates the population-weighted density of 53 Australian, European, and Canadian cities with a population over 1 million, plus the three largest New Zealand cities (only Auckland is over 1 million population). It also shows a breakdown of the densities at which these cities’ residents live, and includes a set of density maps with identical scale and density shading.

Why Population Weighted Density?

As discussed in previous posts, population-weighted density attempts to measure the density at which the average city resident lives. Rather than divide the total population of a city by the entire city area (which usually includes large amounts of sparsely populated land), population weighted density is a weighted average of population density of all the parcels that make up the city. As I’ve shown previously, the size of the parcels used makes a big difference in the calculation of population-weighted density, which makes comparing cities difficult internationally.

To overcome the issue of different parcel sizes, I’ve used kilometre grid population data that is now available for both Europe and Australia. I’ve also generated my own kilometre population grids for Canadian and New Zealand cities by proportionally summing populations of the smallest census parcels available.

Some measures of density exclude all non-residential land, but the square kilometre grid approach means that partially populated grid parcels are counted, and many of these parcels will include non-residential land, and possibly even large amounts of water. It’s not perfect, particularly for cities with small footprints. For example, here is a density map around Sydney harbour (where light green is lower density, dark green is medium density and red is higher density):

Sydney harbour

You can see that many of the grid cells that include significant amounts of water show a lower density, when it fact the population of those cells are contained within the non-water parts of the grid cell. The more watery cells, the lower the calculated density. This is could count against a city like Sydney with a large harbour.

Defining cities

The second challenge with these calculations is a definition of the city limits. For Australia I’ve used Urban Centre boundaries, which attempt to include contiguous urbanised areas (read the full definition). For Europe I’ve used 2011 Morphological Urban Areas, which have fairly similar rules for boundaries. For Canada I’ve used Population Centre, and for New Zealand I’ve used Urban Areas.

These methodologies tend to exclude satellite towns of cities (less so in New Zealand and Canada). While these boundaries are not determined in the exactly the same way, one good thing about population-weighted density is that parcels of land that have very little population don’t have much impact on the overall result (because their low population has little weighting).

For each city, I’ve included every grid cell where the centroid of that cell is within the defined boundaries of the city. Yes that’s slightly arbitrary and not ideal for cities with dense cores on coastlines, but at least I’ve been consistent. It also means some of the cells around the boundary are excluded from the calculation, which to some extent offsets the coastline issues. It also means the values for Australian cities are slightly different to a previous post.

All source data is dated 2011, except for France which is 2010, and New Zealand which is 2013.

Comparing population-weighted density of Australian, European, Canadian and New Zealand cities

AU EU CA NZ Population Weighted Density

You can see the five Australian cities are all at the bottom, most UK cities are in the bottom third, and the four large Spanish cities are within the top seven.

Sydney is not far below Glasgow and Helsinki. Adelaide, Perth and Brisbane are nothing like the European cities when it comes to (average) population-weighted density.

Three Canadian cities (Vancouver, Toronto and Montreal) are mid-range, while the other three are more comparable with Australia. Of the New Zealand cities, Auckland is surprisingly more dense than Melbourne. Wellington is more dense that Vancouver (both topographically constrained cities).

But these figures are only averages, which makes we wonder…

How much diversity is there in urban density?

The following chart shows the proportion of each city’s population that lives at various urban density ranges:

AU EU CA NZ urban density distribution

Because of the massive variations in density, I had to break the scale interval sizes at 100 persons per hectare, and even then, the low density Australian cities are almost entirely composed of the bottom two intervals. You can see a lot of density diversity across European cities, and very little in Australian cities, except perhaps for Sydney.

You can also see that only 10% of Barcelona has an urban density similar to Perth or Adelaide. Which makes me wonder…

Do many people in European cities live at typical Australian suburban densities?

Do many Europeans living in cities live in detached dwellings with backyards, as is so common in Australian cities?

To try to answer this question, I’ve calculated the percentage of the population of each city that lives at between 10 and 30 people per hectare, which is a generous interpretation of typical Australian “suburbia”.

AU EU CA NZ cities percent at 10 to 30 per hectare

It’s a minority of the population in all European cities (and even for Sydney). But it does exist. Here are examples of Australian-style suburbia in outer Hamburg, Berlin, LondonMilan, and even Barcelona (though I hate to think what some of the property prices might be!)

How different is population-weighted density from regular density?

Now that I’ve got a large sample of cities, I can compare regular density with population weighted densities (PWD):

PWD v regular density 2

The correlation is relatively high, but there are plenty of outliers, and rankings are very different. Rome has a regular density of 18, but a PWD of 89, while London has a regular density of 41 and PWD of 80. Dublin’s regular density of 31 is relatively close to its PWD of 47.

Wellington’s regular density is 17, but its PWD is 49 (though the New Zealand cities regular density values are impacted by larger inclusions of non-urbanised land within definitions of Urban Areas).

So what does the density of these cities look like on a map?

The following maps are all at the same scale both geographically and for density shading. The blue outlines are urban area boundaries, and the black lines represent rail lines (passenger or otherwise, and including some tramways). The density values are in persons per square kilometre (1000 persons per square kilometre = 10 persons per hectare). (Apologies for not having coastlines and for some of the blue labels being difficult to read).

Here’s Barcelona (and several neighbouring towns), Europe’s densest large city, hemmed in by hills and a coastline:

Barcelona

At the other extreme, here is Perth, a sea of low density and the only city that doesn’t fit on one tile at the same scale as the other cities (Mandurah is cut off in the south):

 

Perth

Here is Paris, where you can see the small high density inner core matches the high density Metro railway area:

Paris

Similarly the dense inner core of London correlates with the inner area covered by a mesh of radial and orbital railways, with relatively lower density outer London more dominated by radial railways:

London

There are many more interesting patterns in other cities.

What does this mean for transport?

Few people would disagree that higher population densities increase the viability of high frequency public transport services, and enable higher non-car mode shares – all other things being equal. But many (notably including the late Paul Mees) would argue that “density is not destiny” – and that careful design of public and active transport systems is critical to transport outcomes.

Zurich is a city often lauded for the high quality of its public transport system, and its population weighted density is 51 persons/ha (calculated on the kilometre grid data for a population of 768,000 people) – which is quite low relative to larger European cities.

In a future post I’ll look at the relationship between population-weighted density and transport mode shares in European cities.

All the density maps

Finally, here is a gallery of grid density maps of all the cities for your perusing pleasure (plus Zurich, plus many smaller neighbouring cities that fit onto the maps). All maps have the same scale and density shading colours.

Please note that the New Zealand and Canada maps do not include all nearby urbanised areas. Apologies that the formats are not all identical.


Are Australian cities becoming denser?

Tue 5 November, 2013

[Updated April 2017 with 2015-16 population estimates. First published November 2013]

While Australian cities have been growing outwards with new suburbia, they have also been getting denser in established areas, and the new areas on the fringe are often more dense than growth areas used to be (see last post). So what’s the net effect – are Australian cities getting more or less dense?

This post also explores measures of population-weighted density for Australian cities large and small over time. It also tries to resolve some of the issues in the calculation methodology by using square kilometre geometry, looks at longer term trends for Australian cities, and then compares multiple density measures for Melbourne over time.

Measuring density

Under the traditional measure of density, you’d simply divide the population of a city by the metropolitan area’s area (in hectares). As the boundary of the metropolitan areas seldom change, the average density would simply increase in line with population with this measure. But that density value would also be way below the density at which the average resident lives because of the inclusion of vast swaths of unpopulated land within “metropolitan areas”, and so be not very meaningful.

Enter population-weighted density (which I’ve looked at previously here and here). Population-weighted density takes a weighted average of the density of all parcels of land that make up a city, with each parcel weighted by its population. One way to think about it is the residential density in which the “average resident” lives.

So the large low-density parcels of rural land outside the urbanised area but inside the “metropolitan area” count very little in the weighted average because of their small population relative to the urbanised areas. This means population-weighted density goes a long way to overcoming having to worry about the boundaries of the “urban area” of a city. Indeed, in a previous post I found that removing low density parcels of land had very little impact on calculations of population-weighted density for Australian cities. However, the size of the parcels of land used in a population-weighted density calculation will have an impact, as we will see shortly.

Calculations of population-weighted density can answer the question about whether the “average density” of a city has been increasing or decreasing. But as we will see below, using geographic regions put together by statisticians based on historical boundaries is not always a fair way to compare different cities.

Population-weighted density of Australian cities over time

Firstly, here is a look at population-weighted density of the five largest Australian cities (as defined by ABS Significant Urban Areas), measured at SA2 level (the smallest geography for which there exists a good consistent set of time-series estimates). SA2s roughly equate to suburbs.

According to this data, most cities bottomed out in density in the mid 1990s. Sydney, Melbourne and Brisbane have shown the fastest rates of densification in the last three years.

What about smaller Australian cities? (120,000+ residents in 2014):

Darwin comes out as the third most dense city in Australia on this measure, with Brisbane rising quickly in recent years into fourth place. Most cities have shown densification in recent times, with the main exception being Townsville. On an SA2 level, population weighted density in Perth hardly rose at all in 2015-16 (a year when 92% of population growth was in the outer suburbs)

However, we need to sanity test these values. Old-school suburban areas of Australian cities typically have a density of around 15 persons per hectare, so the values for Geelong, Newcastle, Darwin, Townsville, and Hobart all seem a bit too low for anyone who has visited them. I’d suggest the results may well be an artefact of the arbitrary geographic boundaries used – and this effect would be greater for smaller cities because they would have more SA2s on the interface between urban and rural areas (indeed all of those cities are less than 210,000 in population).

For reference, here are the June 2014 populations of all the above cities:

Australian cities population 2014

The following map shows Hobart, with meshblock boundaries in black (very small blocks indicate urban areas), SA2s in pink, and the Significant Urban Area (SUA) boundary in green.  You can see that many of the SA2s within the Hobart SUA have pockets of dense urban settlement, together with large areas that are non-urban – ie SA2s on the urban/rural interface. The density of these pockets will be washed out because of the size of the SA2s.

Hobart SUA image

 

 

Reducing the impact of arbitrary geographic boundaries

As we saw above, the population-weighted density results for smaller cities were very low, and probably not reflective of the actual typical densities, which might be caused by arbitrary geographic boundaries.

Thankfully ABS have followed Europe and released of a square kilometre grid density for Australia which ensures that geographic zones are all the same size. While it is still somewhat arbitrary where exactly this grid falls on any given city, it is arguably less arbitrary than geographic zones that follow traditional notions of area boundaries.

Using that data, I’ve been able to calculate population weighted density for the larger cities of Australia. The following chart shows those values compared to values calculated on SA2 geography:

pop weighted density 2011 grid and SA2 australian cities

You’ll see that the five smaller cities (Newcastle, Hobart, Geelong, Townsville and Cairns) that had very low results at SA2 level get more realistic values on the kilometre grid.

You’ll notice that most cities (except big Melbourne and Sydney) are in the 15 to 18 persons per hectare range, which is around typical Australian suburban density.

While the Hobart figure is higher using the grid geography, it’s still quite low (indeed the lowest of all the cities). You’ll notice on the map above that urban Hobart hugs the quite wide and windy Derwent River, and as such a larger portion of Hobart’s grid squares are likely to contain both urban and water portions – with the water portions washing out the density (pardon the pun!). While most other cities also have some coastline, much more of Hobart’s urban settlement is near to a coastline.

But stepping back, every city has urban/rural and/or urban/water boundaries and the boundary has to be drawn somewhere. So smaller cities are always going to have a higher proportion of their land parcels being on the interface – and this is even more the case if you are using larger parcel sizes. There is also the issue of what “satellite” urban settlements to include within a city which ultimately becomes arbitrary at some point. Perhaps there is some way of adjusting for this interface effect depending on the size of the city, but I’m not going to attempt to resolve it in this post.

International comparisons of population-weighted density

See another post for some international comparisons using square km grids.

Changes in density of larger Australian cities since 1981

We can also calculate population-weighted density back to 1981 using the larger SA3 geography. An SA3 is roughly similar to a local government area (in Melbourne at least), so getting quite large and including more non-urban land. Also, as Significant Urban Areas are defined only at the SA2 level, I need to resort to Greater Capital City Statistical Areas for the next chart:

This shows that most cities were getting less dense in the 1980s (Melbourne quite dramatically), with the notable exception of Perth. I expect these trends could be related to changes in housing/planning policy over time. This calculation has Adelaide ahead of the other smaller cities – which is different ordering to the SA2 calculations above.

On the SA3 level, Perth declined in population-weighted density in 2015-16.

When measured at SA2 level, the four smaller cities had almost the same density in 2011, but at SA3 level, there is more separating them. My guess is that the arbitrary nature of geographic boundaries is having an impact here. Also, the share of SA3s in a city that are on the urban/rural interface is likely to be higher, which again will have more impact for smaller cities. Indeed the trend for the ACT at SA3 level is very different to Canberra at SA2 level.

Melbourne’s population-weighted density over time

I’ve taken a more detailed look at my home city Melbourne, using all available ABS population figures for the geographic units ranging from mesh blocks to SA3s inside “Greater Melbourne” (as defined in 2011) or inside the Melbourne Significant Urban Area (SUA, where marked), to produce the following chart:

Note: I’ve calculated population-weighted density at the SA2 level for both the Greater Capital City Statistical Area (ie “Greater Melbourne”, which includes Bacchus Marsh, Gisborne and Wallan) and the Melbourne Significant Urban Area (slightly smaller), which yield slightly different values.

All of the time series data suggests 1994 was the turning point in Melbourne where the population-weighted density started increasing (not that 1994 was a particularly momentous year – the population-weighted density increased by a whopping 0.0559 persons per hectare in the year to June 1995 (measured at SA2 level for Greater Melbourne)).

You’ll also note that the density values are very different when measured on different geographic units. That’s because larger units include more of a mix of residential and non-residential land. The highest density values are calculated using mesh blocks (MB), which often separate out even small pockets of non-residential land (eg local parks). Indeed 25% of mesh blocks in Australia had zero population, while only 2% of SA1s had zero population (at the 2011 census). At the other end of the scale, SA3s are roughly the size of local councils and include parklands, employment land, rural land, airports, freeways, etc which dilutes their average density.

In the case of SA2 and SA3 units, the same geographic areas have been used in the data for all years. On the other hand, Census Collector Districts (CD) often changed between each five-yearly census, but I am assuming the guidelines for their creation would not have changed significantly.

Now why is a transport blog so interested in density again? There is a suggested relationship between (potential) public transport efficiency and urban density – ie there will be more potential customers per route kilometre in a denser area. In reality longer distance public transport services are going to be mostly serving the larger urban blob that is a city – and these vehicles need to pass large parklands, industrial areas, water bodies, etc to connect urban origins and destinations. The relevant density measure to consider for such services might best be based on larger geographic areas – eg SA3. Buses are more likely to be serving only urbanised areas, and so are perhaps more dependent on residential density – best calculated on a smaller geographic scale, probably km grid (somewhere between SA1 and SA2).

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The growth of Melbourne 1986-2011, animated

Tue 29 October, 2013

Following on from my recent post about the changing socio-economic landscape of Melbourne, this post simply looks at the changing shape and density of urban Melbourne using 5-yearly census data at collector district (1986-2006) and SA1 level (2011).

Straight to it: here is map of Melbourne residential density, click to enlarge and animate:

Melb CD SA1 density

You can see the sprawl of Melbourne over the years, including changes that suggest shifts in the urban growth boundary after development previously seemed to have stopped against a line (particularly evident on the western edge of the City of Brimbank).

Here is another animated map showing the inner city area, with a density scale ranging from 10 to 100 persons/ha, so you can distinguish higher densities than the map above. Click to enlarge and animate.

Melb inner density

You can see a lot more going on in established areas on this map, including densification in the CBD, St Kilda, St Kilda Road (conversion from office space), Parkville, Port Melbourne around Bay Street, Kensington Banks, Brunswick, Fitzroy, Southbank, South Melbourne, Elwood, Maribyrnong, Carlton, and many more.

A few things to note:

  • The size of the districts changes each year, particularly around the fringe. You’ll often see a large red patch where a larger block is only partly inhabited in one year, only to be replaced by smaller denser patches in future years. Patches of green that disappear might be the enlargement of a district causing a blending out of a small pocket of high density, rather than an actual drop in density.
  • Shades of pink indicate densities between 5 and 10 per hectare on the large map, and between 10 and 20 per hectare on the inner map. Lower densities are shown as white.
  • In 2011 the ABS changed their statistical geography. I have used SA1s from 2011 as the most comparable area unit to a census collector district, however they are generally smaller and so densities may appear to jump slightly in 2011 in some areas.

See also earlier posts for: