Where is Melbourne’s ‘centre of gravity’ ?

Change in the 'centre of mass' of employment in Melbourne, 1981-2006

We’re familiar enough with the idea of the ‘centre of gravity’ of population in Melbourne. But where is the centre of gravity of employment?

Is it the city centre? No, for one thing the CBD’s only got around 15% of all metropolitan jobs. For another, the combination of Melbourne’s distinctly lop-sided growth south of the Yarra and the fact that 72% of jobs are more than 5 km from the CBD, suggests it’s going to be somewhere south east of the CBD.

So I’ve calculated the location of the centre of gravity (more correctly, the ‘centre of mass’) of jobs from Census data. The accompanying chart shows how that location changed over the period from 1981 to 2006.

The centre of gravity is calculated by dividing Melbourne up into 1,000 traffic zones and weighting the coordinates of the centroid of each zone by the number of jobs it holds. If you imagine a relief model of employment in Melbourne, the centre of gravity is where you’d rest the model on a needle so that it balancess perfectly.

In 1981, the centre of mass of employment was 5.9 km east south east of the CBD, on Kooyong Rd, just north of Toorak Rd. By 2006 it was 7.9 km from the CBD, close to the corner of Malvern and Tooronga Rds.

This movement reflected the much stronger growth in jobs in the suburbs over this period compared to the CBD and inner city.

Virtually all of that movement occurred over the fifteen years between 1981 and 1996. However between 1996 and 2006, it pretty well stayed put. This wasn’t because jobs grew relatively stronger in the west and north from 1996 but rather because jobs in the inner city stopped declining and started to grow.

Inner city job growth was very strong over the ten years to 2006, especially when compared to its long run decline since at least the early 70s. This is sometimes interpreted as evidence that the inner city, benefitting from the shift toward a more knowledge-intensive economy, assumed a more dominant role in the metropolitan area’s employment market.

That’s incorrect. The reality is that for the first time in years, jobs growth in the inner city was vigorous enough to keep pace with growth in the suburbs, enabling it to hold – but not increase – its share of metropolitan employment. The 2011 Census will give us reliable information on whether or not the inner city has finally regained the upper hand from the suburbs.

The clear and unmistakeable message, though, is that the great bulk of Melburnians not only live in the suburbs but work in them too. Policy that doesn’t recognise that reality is doomed to fail.

The CBD and inner city nevertheless have distinctly different economic functions from the suburbs. I’ll look at that soon.

12 Comments on “Where is Melbourne’s ‘centre of gravity’ ?”

  1. Chris says:

    Nice Analysis, No wonder there’s crowding on the Frankston Line.
    So how does this affect traffic? Are we driving further to get to work?

    • Alan Davies says:

      Can’t lay my hands right now on any data that specifically addresses historical journey to work distance by car in Melbourne, but the general trend has been for the median commuting distance by car to get longer while the median duration remained constant. Perhaps someone else can help.

  2. brisurban says:

    A more risque analysis could ask, where is the centre of Un-employment and why??

  3. Joseph says:

    The 85% of jobs being outside the CBD is an insightful statistic and makes you wonder why the emphasis of transport policy is always so CBD centric. Is it because the 15% in the CBD have most of the political influence? Should more be done to improve flow of traffic in the suburbs rather than proposing billion dollar rail tunnels for the CBD?

    I am interested to know how the 85% figure is calculated. Are Docklands and Southbank in the 85% when really they look much like the CBD? And does the census data correctly record location of actual work? For example, I imagine there is plenty of construction work in the city done by contractors who have registered addresses in the suburbs.

    • Alan Davies says:

      In 2006, 10.9% of metro jobs were located in zones with a centroid that lay within one km of the centre and 15.9% were within 2 km. The latter is a generous definition of the CBD and includes everything you mention.

      The ‘centre’ is defined as the centroid of the zone bounded by Swanston, Collins, Elizabeth and Bourke streets i.e. midway on Lt Collins.

      Note a slight difference – these figures are based on 1,950 zones for the metro area whereas the calculations in the original post are based on 1,000 zones (I needed to use 1,000 zones to get the historical perspective).

  4. Alan, another great post…here is an extract from something I wrote a few years back about urban myths, with myth #5 (our of seven) being that most jobs are downtown…most town planners (I am a planner so I can somewhat get anyway with the criticism) however think that is the case and our cities are being planned as such…

    Myth #5 – Not all jobs are downtown.

    There is also a widespread presumption that central business districts and their immediate surrounding fringes contain the majority of jobs in a city’s economy, and are therefore the major generator of traffic. Developing housing further from the downtown area, the argument goes, will only mean more congestion as commuters try to get into, and out off, the downtown area.

    It is easy to understand how this myth developed – the CBD/fringe holds the tallest buildings in the city; the seat of government is often located there; so, too, are many cultural facilities; they are the hub of train/tram networks and the focus of much of our angst about traffic congestion. We are reminded of the apparent importance of the downtown area every time we watch the TV news – the CBD skyline acts as a backdrop for newsreaders. So, the CBD is often in our minds.

    But downtown is home to around 20% of all jobs in a city’s metropolitan area (just 10%, when looking at the CBD alone). So 80% of our jobs are actually outside of the downtown area. The implications of this are profound. Our ten friends from academia are proposing a policy based on a myth: that urban dispersal of housing will mean longer commutes to work.

    The facts are that most commutes within a city are across suburbs and not downtown. Unfortunately, this type of travel (and the nature of the work involved) makes it impossible to service efficiently via public transport.

    So in truth, more housing on the urban fringe will not in itself lead to more inner-city congestion, but will produce more suburb-to-suburb work trips. Perhaps as a priority (and in concert with more decentralisation and suburban development), we should build better ring-road systems (and more river crossings in Brisbane), rather than advocating mostly infill redevelopment and heavy urban infrastructure spending.

  5. Sam says:

    Interesting to know that I ride through the centre on my way to work (in the CBD) when I got the long way – which involves riding away from the CBD and then turning around.

    Living roughly near the centre of mass for employment over the last two years, it has occurred to me that the city needs a north-south mass transit option through this area.

  6. brisurban says:

    “The facts are that most commutes within a city are across suburbs and not downtown. Unfortunately, this type of travel (and the nature of the work involved) makes it impossible to service efficiently via public transport.”

    I think that its only impossible insofar as we continue to focus on the CBD commuter as the public transport market. The Melbourne SmartBus is a radial bus network that gets quite good patronage. So I don’t think it is impossible.

    It would be interesting to see how the city of Toronto copes with this issue- their buses run cross-town, only a few actually enter their CBD from what I can gather.

    Brisbane needs a few key river crossings, but the river is more of a barrier to cars because we have the CityCat which runs on the river. The phenomenal amount of people cycling, walking and catching buses over the Eleanor Schonell Bridge at Dutton Park, Brisbane might give an indication of how to exploit these strategic bottlenecks to give public transport absolute advantage.

  7. Rose says:

    Just wondering why there are so many high-rise apartments currently built in the CBD if they are not for meeting with increasing jobs or overseas students.

    • Alan Davies says:

      While the CBD’s and inner city’s share of metropolitan jobs was constant over 1981-06, jobs nevertheless grew in absolute terms in the centre. Since 2006 absolute job growth in the centre appears to have been even more vigorous.

      But jobs don’t necessarily have to grow in the centre in order for demand for CBD apartments to increase. Could be explained simply by changing housing preferences of inner city workers. Another explanation is that its an attractive location even for people who don’t work in the centre i.e. those who reverse commute.

  8. […] 28% of jobs were within 5 km radius and the ‘average job’ was now 15.6 km from the centre. The centre of mass had moved 2 km further outwards to the vicinity of Tooronga, 7.9 km from the CBD. Proportion of […]

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