Tauranga and Whakatane have been New Zealand's fastest growing towns over the past 80 years, as Kiwis followed the sun to the country's sunniest places.
A long-term analysis by economists from the Motu consulting group and Auckland University has found that sunshine hours were one of four main factors driving the growth and decline of 56 NZ towns from 1926 to 2006, along with the quality of the local agricultural land, local educational levels and proximity to the country's biggest city, Auckland.
Auckland itself was only the eighth-fastest-growing town over the 80 years, but it grew much faster than the three others of what were the four main centres in 1926 (Auckland, Wellington, Christchurch and Dunedin), so its faster growth helped to pull up other towns in the northern North Island.
All but one of the 10 fastest-growing towns were in the upper North Island. Levin, also a sunny spot just north of Wellington, was the sole exception.
Whakatane, with 2704 sunshine hours last year, is officially New Zealand's sunshine capital. The National Institute of Water and Atmospheric Research (Niwa) lists Blenheim as the sunniest of 27 other towns that it tracks, with an average 2475 sunshine hours a year between 1981 and 2010, followed by Nelson (2472), Lake Tekapo (2417) and Tauranga (2345).
The next two fastest-growing towns after Whakatane and Tauranga also have more sunshine hours: Rotorua (2127) and Hamilton (2020), compared with 2003 hours in Auckland.
In contrast, the 10 slowest-growing towns were mostly in the colder South Island. The slowest-growing town was the coal-mining town of Kaitangata in south Otago, which lost an average of almost 1 per cent of its population every year over the 80 years.
Motu economist Eyal Apatov said the differential growth rates were due to a mix of productivity-related and lifestyle factors, with sunshine hours largely in the lifestyle category.
"Sunshine hours can attract people to live in places like Nelson because of its high amenity, not because of high wages," he said.
Not surprisingly for a farm-based economy, the study found that local land-use capability was another key growth driver for towns such as Hamilton, Pukekohe and Cambridge.
The three Bay of Plenty towns that topped the list, Tauranga, Whakatane and Rotorua, have been associated with the growth of the forestry industry, especially in the first half of the 80-year period up to 1966 when other towns in the Auckland Province grew much faster than Auckland itself. But another co-author Dr Arthur Grimes said forestry land was counted in the model as having a lower land-use capability, so forestry did not have a big impact on population trends overall.
He said Auckland grew much faster than the other three original main centres partly just because it was the biggest to start with. In 1926 it had about 200,000 people compared with about 130,000 each in Wellington and Christchurch. By 2006 it had 1.2 million people compared with under 400,000 in both the other two centres.
"It's all part of the agglomeration story where a bigger city is more productive, and being closer to the big city makes you more productive," Dr Grimes said.
"New Zealand is a small place. We have one large city, which is Auckland. But Auckland is only the fifth-largest city in Australasia, so it's quite small, so there is probably only room for one medium-sized city in New Zealand."
He said Auckland's growth fed the growth of towns in the rest of the northern North Island through factors such as Aucklanders holidaying and retiring close to home.
The study also found some evidence that more education drove faster growth of towns recently, but it was unable to find comparable data for earlier years so it used the Maori percentage of the population as a "proxy" because of a close relationship between more Maori people and lower average education levels.
However Mr Eyal said the effect of a lower Maori population as a driving force for faster growth might actually reflect official discrimination against areas of high Maori population in the early years, citing an 1880 commission which recommended against building railways in areas "in the hands of the Natives".