I spent a little time this afternoon trying to get hold of data. I guess I have high expectations that the web should deliver what I want instantly; in the old days it would have taken a few days in the library to track down the data sets I needed, and then a few weeks waiting for it on inter-library loan. In some respects, things haven’t changed much, although now it just means you hit the paywall faster. Here’s today’s tale…
It began with a post by George Monbiot on how we’ll have to make cities much more dense if we are to cut down their energy needs. George then tweeted about a fabulous graph from the UNEP which illustrates the point nicely:
In which Toronto holds an interesting position compared to other North American cities. Anyway, someone then pointed out that this data is a little old – it’s based on a classic study by Newman and Kenworthy from the 1980’s. So now the hunt begins: is there an updated version of this anywhere, and if not, can I get hold of the data to create it?
Luke Devlin tweeted out a newer version, published in 2009, based on data from the UITP Mobility in Cities Database, which has data from around the year 2001:
However, this graph is pretty ugly, and has none of the cities labelled. So, methinks that would be easy to fix – all I need is the data. Unfortunately the database (on CD-ROM – how quaint!) costs €1,200. And I’d have to wait for it to arrive. Surely someone has this online for free? No? After all, I only want to use one indicator…
Okay, so the data hunt is on. Population density data is easy to get hold of – wikipedia has plenty of it. In exploring this a little, I find some wikified concerns expressed about the original graph, and a whole can of worms about how exactly you compute population density for a city (tl;dr: it depends where you think the city boundaries are).
A little more googling turns up a fascinating 2003 paper “Transport Energy Use and Greenhouse Gases in Urban Passenger Transport Systems: A Study of 84 Global Cities” (by the same Kenworthy), which has a graph of exactly the data I need:
But of course, it points me back at the same UITP dataset for the actual numbers. Darn.
Then there’s a UNEP report dated March 2011, “Technologies for Climate Change Mitigation – Transport Sector“, which uses the same data, but actually does plot the graph I’m after:
It’s a little better than the previous version, but still doesn’t label the individual cities (which one is Toronto??). And of course, although the report is dated 2011, it’s still the same 2001 dataset from UITP.
So where else might I get data like this? A little more googling and I hit what looks like the jackpot: An extensive list of resources on transportation statistics. Unfortunately, the only one that seems to have the transport data by city is the UITP dataset. Back to that paywall again.
In the meantime, I seem to have launch George Monbiot off into an investigation of the academic publishing racket, exploring why the results of publicly funded research is invariably behind a paywall:
I look forward to reading his blog post on that topic. Meanwhile, I’m off to track down someone on campus who might already have the UITP CD-ROM…
Update 4-Jul-2011: Chris Kennedy sent me his 2009 paper in which he did a detailed analysis for 10 cites, with an update of the density vs transport energy consumption curve. He tells me he has the energy data for more cities, but not the density data, as this is very hard to do consistently. Oh, and silly me – I’d already blogged this, together with Chris’ graph last year. Here’s Chris’s graph. He says “The logarithm of urbanized density has a statistically significant fit (t stat ) -10.26) against the logarithm of GHG emissions from transportation fuels with an R2 of 0.93 (Table 2). The logarithm of average personal income is statistically insignificant (t stat ) -0.35).” (p7299)
Chris also tells me the IEA report on the world’s energy, due out later this year, will chapter on cities, with an update of the graph.
