Charting Transport

Is the rate of car ownership still growing in Australia?

Firstly, by car ownership rate I mean the ratio of the number of registered “passenger vehicles” (from the ABS Motor Vehicle Census) to population (also from ABS). Of course some of these cars are owned by companies and not garaged at households, but the data is what it is.

When looking over the last 23 years, it is no surprise to see car ownership rates in Australia have risen considerably:

(click on the chart for a less blurry version)

What is interesting in this chart is the relative rate of car ownership between states and territories. The Northern Territory is consistently the lowest – I’m guessing related to the relatively large indigenous population. I’m not sure for the reasons for other differences. It may be the percentage of the population that is in big cities and the car mode share of those cities. It might also be slight differences in reporting from the state agencies (see ABS’s explanatory notes).

But what about the most recent trends? Here is the same data zoomed in to the last 8 years:

It appears car ownership has more or less levelled-out in a few states:

• Victoria, between 2006 and 2010
• Western Australia, from 2007 onwards
• Queensland, from 2008 onwards (it has actually declined very slightly)

This is fairly consistent with other evidence about declining car use and mode shift to public transport in Australia’s cities.

And the overall rate for Australia appears to have levelled out between 2008 and 2010.

Are cars getting cheaper?

Certainly motor vehicles have been getting cheaper in real terms since around 1996 (relative to overall CPI). They’ve also actually been getting cheaper in nominal dollar terms since 1995.

You might have thought increasing affordability was a strong driver of car ownership rates, but it doesn’t explain growth in car ownership pre 1995, or the slowing of car ownership rates around 2008.

What about usage of each car?

Using data from the BITRE 2011 yearbook, it is possible to calculate an estimated annual kms per passenger car. For this I’m comparing the number of vehicles at the motor vehicle census date with an estimate of total car kms in the previous 12 months (straight line interpolation of BITRE year ending June figures). This isn’t a perfect measure as the number of cars grows throughout the 12 month period where kms are taken, but it is still a guide to the trend.

That’s a pretty clear downwards trend, particularly in recent years.

What might explain this?

• From 1995 to 2005 cars have become more affordable and so we can own more cars and need to share them less.
• From 2005 to 2010 car ownership rates have slowed and we are driving cars less as we travel less and/or shift to other modes.

What about car ownership in cities?

The data available on the ABS website is only available at the state and postcode level (and at postcode level only for recent years). However with some GIS calculations I’ve been able to come up with an estimate of the number of passenger cars with an owner address within the Melbourne Statistical Division (postcode boundaries sometimes do not perfectly align with the Melbourne SD boundary on the fringe, but this is fairly minor and mostly in rural postcodes).

Here is a chart comparing Melbourne, Victoria, and Australia:

So after quite a bit of work extracting and processing all the data, I’ve found very little difference between the Melbourne and Victoria rates or trends. Which does seem a little odd given it is probably easier to live without a car in Melbourne than the rest of the state. It might be that there are many cars with an ownership address in Melbourne, but garaged outside Melbourne. I’m not sure (anyone know more?).

I have covered the spatial variations of car ownership in Melbourne in another post.

What about motorcycles?

Are more people owning motorcycles instead of cars?

You can see motorcycle ownership rates have grown significantly since around 2004 (although still very small).

Does it explain the slowdown in the car ownership rate?

This chart still shows a slow-down after 2008, so it doesn’t look like rising motorcycle ownership explains the car ownership slow-down. Motorcycle ownership took off in 2004, but car ownership slowed in 2008.

What about the ageing population?

Could the data be impacted by a changing age profile? Very old people are probably less likely to drive and hence own a car, so maybe this would lead to a declining car ownership rate per head of population as a greater portion of the population is older.

Suppose most car owners are aged 18 to 80 years. Here’s the percentage of Australia’s population within that age band:

The share has been very steady at around 73 to 74% for all of the last 16 years, which suggests little impact on overall car ownership rates.

Then again, those aged 80 today might be healthier and/or wealthier and more likely to own cars that those aged 80 in 1994. In that case, the rate of car ownership of younger people would have seen less growth, but this is purely speculation and I’m not aware of any available data that could enable a test of this hypothesis.

Notes on the data:

• The ABS Motor Vehicle Census has been taken in different months in different years. State population estimates are only available on a quarterly basis. I have used the nearest quarterly population figure for each motor vehicle census where they do not align (never more than one month out).
• Melbourne population estimates are only available at June each year. I have used straight line interpolation of passenger car figures to produce a June estimate of passenger cars per capita for each year (same as for annual car kms).

This entry was posted on Sunday, August 7th, 2011 at 11:53 pm and is filed under Car ownership, Melbourne, Mode shift, Pricing. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.