A couple of weeks ago I wrote about some of the similarities and differences between New Zealand’s largest cities. At one point I reported that the population of Wellington was larger than that of Christchurch based on Wikipedias 2017 estimates, but then further down I had a population graph based on 2013 Census data which showed that Christchurch was bigger, at least if you use a cut-off 30km from the city centre.
This was picked up on Twitter and initiated a bit of debate betwen Wellingtonians and Cantabrians.
So I created a new cumulative population graph showing only Christchurch and Wellington, and I extended it out past 30km to capture the entire urban agglomerations for both cities. Here is the resulting graph with cumulative population on the Y-axis, kilometres from city centre on the X-axis.
It shows that, if you draw your cut-off at shorter distances like 30-40km, then Christchurch has a significantly larger population than Wellington. Beyond this Wellington starts to catch up, and eventually overtakes Christchurch at about 67km due to having a few larger towns up the Kapiti Coast and Wairarapa.
I think it’s debatable whether towns 60-80km away should be considered part of Wellington or Christchurch. In both cases the urban fabric definitely stops prior to this, with large swathes of farmland or forest, before starting up again at each small town. Granted there are some people live this far away and commute in – a friend of a friend lived in Masterton and commuted into Wellington for work every day, and I once worked with someone who lived in Ashburton and commuted into Christchurch. But these super-commuters are exceptions and I suspect there would only be a very small number doing this. I don’t think it’s enough to justify calling Masterton and Ashburton parts of Wellington and Christchurch.
In conclusion, I think it’s fairly safe to say that Christchurch has a larger population than Wellington. Or at least it did in 2013 – now we just have to wait for the 2018 census data to see if this has changed or not.