A century-long population drift to the north has gone into reverse.
A Statistics New Zealand report on internal migration shows that a net 10,300 people moved from the North Island to the South Island in the five years before the 2006 census.
The Auckland region alone lost a net 18,000 people. This was still dwarfed by 66,000 immigrants coming into Auckland from overseas, but the figures suggest that some immigrants now use Auckland as a staging post from which to move to other regions.
Economist Phil McDermott said the figures confirmed that New Zealand was seeing the same trend towards decentralisation that had been evident in the United States since the 1970s, as an older and technologically wired population escaped the cities.
The biggest magnets for migrating Kiwis were the Bay of Plenty and Waikato, including Coromandel, and, in the South Island, Canterbury and Otago, including Queenstown.
"There is a growing movement now towards lifestyle localities," Dr McDermott said.
"This is not just influencing the empty-nesters and people moving towards retirement.
"Young families are realising that there are job opportunities in the provinces, whether by remote working or because the smaller centres are increasingly buoyant."
Auckland still dominates New Zealand's population, accounting for 32 per cent of the population in the 2006 census and 50 per cent of the growth since 2001.
But this is now solely because of the inflow from overseas and an excess of births over deaths.
New Zealand's population has been drifting north since the end of the land wars in the 1860s opened up the North Island to European settlement after a period when gold rushes and freely available land attracted most migrants to the south.
Dr McDermott said more people from southern parts moved to Auckland than moved away from 1900 to 1996 except for three years during the 1930s Great Depression, a brief period after World War II and three years in another recession around 1980.
This pattern was broken for the first time with a net outflow from Auckland to the rest of the country of just under 2000 in the five years to 2001.
In the next five years, to 2006, the exodus accelerated to a net loss of 18,000.
Allowing for immigrants who did not say where they were going, Dr McDermott estimates migration from overseas accounted for two-thirds of Auckland's total population growth between 2001 and 2006.
"Any slowdown in migration will have a disproportionate impact on Auckland's growth," he said.
He said the dairying boom was a factor in the growth of areas such as Waikato and Canterbury, but New Zealand's manufacturing base was also being decentralised.
"There are clear signs that manufacturing has been growing faster in the rest of the northern North Island, like Waikato and Tauranga.
"Where Auckland has retained its dominance is in consumption activities such as retailing, and in business services."
He said Auckland was paying the price of traffic congestion, high housing and living costs and uncertain power supplies.
Overall, the North Island still increased its share of the national population, from 75.7 per cent in 2001 to 76.0 per cent in 2006, because of the influx from overseas.