While New Zealand's population was continuing to grow it was becoming much more concentrated in the main centres, Cameron said. "For a lot of regions it really is about managing the decline."
Declining areas could have a reverse momentum. "You can get young people moving out of the area. You're going to get less natural increase, that's going to reinforce population decline," Cameron said.
Declining rural areas tended to have more older people, while the larger centres had tertiary education opportunities that drew in the young.
"Areas that have more job growth, better income availability, lower unemployment, those tend to be places that are attractive for people to live," he said.
Good amenities were also important. "There's quite a difference between the sorts of things you can do in Auckland from Taumarunui, for instance. People like to be able to be able to do things, and urban centres tend to have more of those opportunities."
Migration was one factor contributing to fast growth in some areas but so was natural increase - the difference between births and deaths.
Although some migrants were retirees, most tended to be younger than average. "Younger people have more babies so that reinforces itself."
Cameron did not expect there would be a tipping point where Auckland's high house prices and traffic congestion would lead to an avalanche of people moving out. "It's a trickle rather than a torrent," he said.
But Auckland's high property prices were benefiting Hamilton and the Waikato District. While some people were commuting north into Auckland, jobs were also spilling over from Auckland into Waikato, where land was much cheaper.
Waikato also had good road and rail links to the ports in Tauranga and Auckland, Cameron said. The dairy boom, although ending 18 months or so ago, had also brought considerable income into Waikato, as well as into Taranaki.
Hamilton did have a similarity with Dunedin that counted against the cities. "They have the university there (Dunedin), which brings in a lot of young people but once they finish they are all heading out of Dunedin. We have the same thing here in Hamilton."
Dunedin's slow growth was a long term trend. It had been New Zealand's largest city in the 19th century and it was hard to pull out the causal factors that had led to its decline in importance.
Queenstown had a booming tourist industry, which was labour intensive, Cameron said. "There's a lot of jobs available. Those jobs pull in people. The more people you have the more hairdressers and things you need. It gets a little bit of momentum going."
Nelson had the same sort of sunbelt migration that Tauranga did, including the arrival of many retired people. Gisborne was "so far away from everywhere. It's very isolated out there."
The notoriety of Wellington's weather didn't seem to be a massive disadvantage, Cameron said. He had looked into the effects of climate on migration, and while it had an effect it wasn't very large.
"People do tend to move to sunny, warmer, less wet places, but the actual size of that effect is pretty small."
Some work had been done on whether regions could arrest population decline by attracting migrants, he said. "But the amount of migration you would need to offset both the ageing population and the fact young people want to move out - it's unrealistic."
Overseas, where areas with declining populations had managed a resurgence, it was usually because of some sort of black swan event. For example, the only thing that turned the population change in North and South Dakota around had been the fracking boom. "It was really a one-off," Cameron said.
One small district that had done a good job of turning around declining fortunes was Otorohanga, which had been losing people for a long time before growing between the last two censuses.
"They managed to retain a lot of their young people," he said. Dale Williams, who was mayor from 2004-2013, had a compact with local employers to make jobs available for young people.
"Because young people could stay in Otorohanga and have a good job, many chose to stay. Then you have more natural increase in the population, as well."Daly did a good job of collecting and summarising my comments. The key point is that the areas that are already growing fast (especially Auckland, Tauranga, and Hamilton - the so-called 'Golden Triangle' of the upper North Island) are doing so not solely because of migration. Migrants tend to be younger than non-migrants (even for Tauranga a lot of in-migration is young people), and younger people generate additional population growth because they have children. At the other extreme, rural and peripheral areas of the country are experiencing sustained out-migration of the younger population, which is a double-blow (again because there will be fewer children as a result). It could be (and may yet become) worse though - consider the situation in Japan.
The idea that there will be 'winners' and 'losers' in future population growth is nothing new. Consider the discussion of 'zombie towns' in New Zealand (which I discussed here). The Marsden funded project Tai Timu Tangata (led by Natalie Jackson, and including me) will begin producing some final outputs over the coming months. I look forward to outlining some of those outputs here.