Every half-decade, Census data gives us an interesting and detailed insight into how New Zealanders are travelling. Back in August, the Ministry of Transport published a comprehensive analysis of journey to work patterns in Auckland (ably summarised by Matt here).
Here’s one of the key maps from the report. It shows average distance travelled to work for all suburbs in Auckland. Blue means shorter trips, red means longer trips. As you can see, average commutes get a lot longer if you live further from the city centre:
(I’ve used the same data to take a look at issues like housing and transport costs and greenhouse gas emissions from commutes in NZ’s large cities. It’s definitely a rich source of insight into how we live.)
The Census journey to work data presents a conundrum. Auckland is not a monocentric city in which all employment is concentrated in the centre. It is in fact highly polycentric, with employment dispersed throughout a number of locations. The map below, which I put together quickly using Statistics NZ’s Business Demography employment data, shows this. There are certainly many jobs in the city centre – around 15% of the total – but employment is spread around the entire Auckland region.
Given this, why aren’t people in outlying areas simply commuting to the nearest jobs, and skipping the long average commutes across town? Why aren’t the residents of Browns Bay commuting to Albany, the residents of Glen Eden to Henderson, and Howickians to East Tamaki? Auckland’s employment has long since decentralised – so why haven’t our travel patterns decentralised as well?
To answer these questions, we must consider the dynamics of urban labour markets. Here’s an illuminating graphic from Alain Bertaud’s recent talk in Auckland, which I reviewed here. It shows four different models for urban labour market, ranging from a totally monocentric city (all jobs in the centre) to a totally dispersed city (all jobs randomly dispersed). Auckland is clearly what Bertaud calls a “composite” city. It has a strong and growing city centre, but also a lot of jobs spread around other metropolitan centres, industrial parks, local shops, etc.
In a composite city, people do not simply commute to the nearest offices – they will actually travel to jobs all throughout the city. The “urban village” idyll simply doesn’t happen in real life. There are three big reasons for this:
- First and foremost, labour markets are dynamic. Even if people start out working near where they live, this happy state of affairs doesn’t necessarily continue. Companies go out of business, workers get offered better jobs elsewhere, and people change careers. This happened to me earlier this year – a job change saw me swap my short commute from Mount Eden to the city centre for a longer commute to Takapuna.
- Second, most households include multiple workers, who may have jobs in very different places. If you’re a baggage handler at the airport married to an accountant who works in Newmarket, it’s not going to be possible to live anywhere that offers you both a five-minute commute.
- Third, people don’t necessarily want to live right next to their jobs. While commute costs are an important determinant of household location choices, we also consider a range of other factors, such as proximity to beaches and parks, school zoning, the location of family and friends, and so on and so forth.
Because labour markets are dynamic and people’s location choices are influenced by a range of factors, average commute distances tend to follow the location of the average job in the city. In other words, if you live in a neighbourhood that is ten kilometres away from the average job, you’d expect your neighbours to commute ten kilometres, on average. Some of your neighbours will have shorter commutes to local jobs, while others will travel longer distances to jobs on the far side of the city.
With that in mind, I’ve calculated the weighted average location of jobs in the Auckland region using Statistics NZ’s Business Demography employment data for 19 high-level industries. (Without going into the details, you can think about the method as follows: Let’s say that one individual industry has 200 jobs in Albany and 100 jobs in Takapuna. Then the weighted average job would be located two-thirds of the way from Takapuna to Albany. That’s what I did, except I was working with data on over 400 Auckland suburbs.)
The following map plots a centre point for each of the 19 industries. It shows that the average job is located in the Auckland isthmus. The average job in “blue collar” industries like manufacturing and warehousing tend to be located much further south – a result of the concentration of those industries in places like Mount Wellington, East Tamaki, and near the Auckland Airport. “White collar” industries like finance and insurance and professional services, on the other hand, are much further north, as they tend to be more centralised in the city centre and, to a lesser extent, in metropolitan centres like Newmarket and Takapuna.
If we look back to the first map, from the Ministry of Transport’s analysis of Census journey to work data, we can see that the geographic centres of Auckland industries fit within the blue swathe of relatively low average commute distances down the middle of the isthmus.
In other words, centrality still matters even in a decentralised city! In a dynamic labour market, it is beneficial to live near the average job because it will tend to minimise expected commute distances over time as you change between jobs. That’s one of the reasons why prices are so high in the most central areas of Auckland: people seem to be paying a premium to be closer to the average job.
Of course, the data in the last map also shows that workers with different skills may have different optimal locations. If you expect to work in a “blue collar” industry, living further south might be a better strategy for minimising your expected commute distances. On the other hand, living further north might be better if you’re expecting to work in office jobs. However, labour markets are dynamic in another way as well – people may retrain or change industries throughout the course of their lives, and children may aspire to different professions than their parents. If that’s the case, living closer to the centre still offers more flexibility.