The company I work for, RCG Ltd, has just released some new research which I’ve been working on over the last few months. It looks at how much Auckland households spend in petrol stations, living in different parts of the city. RCG has released it in a free publication called Constructive Thinking, available here (the PDF is available on that page – subscribing is optional).
I initially presented this research at the NERI Energy Conference in March, but I’d probably suggest reading that second, as it’s a bit more in-depth and may rely on me talking along with the slides to make sense!
I’ve used a data source which I think is pretty neat – EFTPOS spending data, covering all spending in petrol stations by the customers of one of the major banks. It’s an excellent sample of total household driving behaviour, since at least 90% of petrol station sales are made via EFTPOS, and petrol makes up the lion’s share of what households buy at petrol stations.
This research is in a similar vein to that done by Peter Nunns and Mattingly and Morrissey. The major difference is that those studies concentrated on commuting costs – using census data on where people live and where they work. They also consider the entire range of transport costs related to that driving (e.g. car maintenance and depreciation, costs of time), which I haven’t done – I’ve stuck with just the amount spent in petrol stations.
First up, we’ve put together an interactive map, with a full-screen version available from the linked page. This divides Auckland suburbs into five “quintiles”, from low to high spending. As per the image below, the low-spending suburbs have average spending of $2,000 to $3,800 a year, and the high-spending ones are at $5,300 or more.
We used several screenshots from the map in the publication, but I think the one below is especially telling – this shows just Auckland’s growth areas, and how they measure up in terms of spending. Households in Flat Bush, Silverdale and other remote growth nodes are spending plenty on petrol, and of course that’s also got implications for CO2 emissions and Auckland traffic.
Thinking about the whole of Auckland, I was quite surprised at how big the variations were between different suburbs. City fringe suburbs have some pretty high spending, and rural areas are higher again (although not so much for the local towns, i.e. Pukekohe, Warkworth, and Wellsford).
The wealthiest parts of Auckland tend to spend less than $4,000 a year in petrol stations – often much less – compared with the region average of $4,500. The poorest parts of the city, generally in south Auckland, had much higher spending. A back-of-the-envelope analysis would suggest that this is partly due to higher smoking rates (cigarettes being a common in-store purchase), but that hasn’t come through in my regressions, so I’m unsure how big an influence this is. Anyway, this is one of the few topics where you can say that Remuera is lower decile than Mangere…
Another interesting image fits a trend line to average spending in a suburb, based on how far it is from the CBD. There’s a logarithmic relationship, and I note that it’s not necessarily that the CBD is an important factor for households everywhere, but more that distance from the CBD is a good “proxy” indicator of how far households have to drive to access services, employment, shops and so on.
I’ve also done some regression analysis with the data, comparing it against a range of census variables, but I’ll leave that for another post.
Thanks to RCG for supporting this research, NERI for inviting me to present it at the Energy Conference, and Datamine for the underlying spending data.