Myth tested
In November 2008, word reached Statistics New Zealand that a wind of discontent was blowing through Wellington. Media stories were circulating that Christchurch had overtaken Wellington to become New Zealand’s second most populated city, leaving Wellington, to quote one journalist, "absolutely positively third". As phones rang hot in council offices and mayors were briefed, the question on everyone’s lips was ‘which city is largest?’.
In order to answer this question we first need to consider what a city is. According to the definition used by Statistics NZ, a city is a type of territorial authority area. Territorial authority areas are administrative in nature (each area is governed by its own council) and their boundaries are defined in law. Under this definition, Wellington City (as governed by the Wellington City Council) is an area which includes the northern suburbs of Tawa and Greenacres but which excludes urban settlements in nearby Porirua and the Hutt Valley, whereas Christchurch City (as governed by the Christchurch City Council) includes a large urban area as well as the predominantly rural Banks Peninsula.
‘What?’ you may say, and rightly so. When many people use the term 'city' they have in mind a large urban settlement and not an area (such as Christchurch City) which is both urban and rural in character. It’s clear that the official definition of ‘city’ doesn’t sit nicely with some common uses of the term.
It’s partly because of this that Statistics NZ also produces statistics for ‘main urban areas’. These main urban areas have no administrative or legal basis, but are intended to represent the large built-up areas that many people think of as ‘cities’. And they can be quite different from their territorial authority counterparts. As defined at present, the Wellington Urban Area extends over four separate territorial authority areas (encompassing a large proportion of Wellington City as well as Porirua, Upper Hutt and Lower Hutt cities), whereas the Christchurch Urban Area is centred on Christchurch City but also includes the settlements of Kaiapoi (in the neighbouring Waimakariri District) and Prebbleton (in the Selwyn District).
So back to the burning question: which city is larger? If we were to focus on the territorial authority areas known as Wellington and Christchurch cities, Christchurch City has a considerably larger population than Wellington City and has done for some time. Indeed, on the basis of these statistics Wellington City is not NZ’s third largest city at present, it is actually NZ’s sixth largest city (behind Christchurch City, and the northern cities of North Shore, Waitakere, Auckland and Manakau). However, if we focus on main urban areas, we find the estimated resident population of the Wellington and Christchurch main urban areas is very similar at present, with Christchurch (386,100) holding only a slim lead over Wellington (386,000) at 30 June 2009.
Conclusion: This myth is all about semantics
How did this myth arise?
This myth arose because the term ‘city’ means different things to different people.
Late in October 2008, new population estimates were released which showed the estimated resident population of the Christchurch Urban Area had slightly exceeded that of the Wellington Urban Area. It was with reference to these statistics that journalists declared that Christchurch had displaced Wellington as NZ’s second largest city. It was a declaration which caused some confusion though as population estimates for territorial authority areas were also available, and told a quite different story.
When it comes to understanding the distribution of New Zealand’s population both territorial authority and urban area statistics have a role to play. In order to ensure the relevance of future urban area statistics, Statistics NZ will be considering the criteria for defining urban areas during 2010. For information about this review, or to provide feedback, contact geography@stats.govt.nz.
Some facts about the Wellington and Christchurch urban areas:
While the boundaries of the Wellington and Christchurch urban areas have changed over time, the relative population size of these areas has been similar for most of the last century. At the time of the 1926 Census - some 85 years ago - the census night population of Wellington was only 3,300 higher than that of Christchurch.
Under the 2006-base medium projection series produced by Statistics NZ in 2008, the Christchurch Urban Area (with average annual population growth of 0.6 percent) is projected to grow slightly faster than its Wellington counterpart (0.5 percent) over the next two decades.
The estimated resident population of urban areas is related, in part, to how and where urban boundaries are drawn. Lying on the outskirts of both the Wellington and Christchurch urban areas are a number of rapidly growing settlements (Paraparaumu and Waikanae for Wellington; Lincoln, Rolleston and West Melton for Christchurch). Future decisions about where urban boundaries begin and end may well determine which urban area holds the mantle of 'NZ's second largest'.