KEY POINTS:
The numbers shake our sense of national identity: 800 New Zealanders a week packing up to live in Australia; "permanent" departures topping 80,000 a year - half of them heading across the Tasman. And most, around 70 per cent, are New Zealand-born.
Long-term departures of New Zealand citizens have run at historically high levels in each of the last four years and Australia is taking a growing proportion of them - nearly 70 per cent in the year ended June 30 compared to 53 per cent five years ago.
In the 2006 Australian Census, 389,465 Australian residents identified themselves as born in New Zealand, equivalent to 9 per cent of our population and 12 per cent of the NZ-born population currently living here. The total number of people with New Zealand citizenship living across the Tasman may top 450,000.
Monthly migration figures updated by Statistics NZ are reliable fodder for Opposition MPs who, like clockwork, link them to high taxes and Labour's economic mismanagement. Figures for the year to March 30 were no exception - National immigration spokesman Lockwood Smith: "The future of this country is fleeing in droves." For the year ended June 30, the numbers rose again.
The last-one-out-turn-out-the-lights bogey understandably raises public and political concern. But the reality of New Zealand's migratory pattern is more complex, and more circular, say population experts. And tax cuts and pay rises aren't likely to stop people leaving or bring them home.
While the numbers departing long-term for Australia are eye-popping, it's clear that many don't stay there long-term. About a third come back within five years, others continue their global migration. They are a restless bunch, Kiwis who fly.
Many more come home as they get older and career goals change. They see advantages in New Zealand's wide open spaces, or decide to raise families in an environment similar to the one they grew up in.
"There's a huge amount of circularity in the movement between Australia and New Zealand, in both directions," says Graeme Hugo, professor of geography at Adelaide University. "It's wrong to think of it as an exodus from New Zealand to Australia, it's really quite a vigorous flow in both directions."
A downturn in Australia's economic fortunes - particularly in the mining industry - could stem the tide, if not reverse the flow.
As long as incoming migrants exceed outgoing, does the current exodus to Australia matter? The Government cites Labour Dept research that - rather than suffering a brain drain - New Zealand is gaining in skills: arriving migrants are better qualified and more experienced than those leaving.
But don't forget, says Professor Richard Bedford of Waikato University, around 85 per cent of the population born in New Zealand are still here. About 600,000 NZ-born are estimated to be living overseas while the 2006 Census counted the NZ-born population living here at 3.26 million.
"I don't have the nervousness that people have that somehow we're going to lose everybody to Australia," says Bedford, head of the university's population studies centre. "An awful lot of New Zealanders actually like living in New Zealand.
"We have to ask the question: why haven't more of the people born in New Zealand gone to Australia? The stayers are by far the predominant group. It's much too soon to start thinking everybody's going and we're going to be running out of people."
Past exoduses - in the late-70s, late-80s and late-90s - have been linked to New Zealand's relative economic fortunes. But the current wave coincided (until recently) with a period of economic buoyancy and historically low unemployment. Clearly, say the experts, New Zealanders are not being driven out by the state of our economy.
"You can't predict it solely on the basis of economic cycles," says Bedford. "The flow to Australia began to pick up in 2003-04 when we had quite significant labour shortages at home."
Statistics New Zealand principal demographer Mansoor Khawaja suspects the current exodus is linked more to pull factors in Australia - where the mining boom has drawn workers out of main centres creating skill shortages, as well as better weather and lifestyle - than push factors here, such as student loans.
Nevertheless, anecdotal feedback from expats suggests higher salaries are keeping many overseas for longer.
But higher wages don't necessarily translate to better living standards - factors additional to income levels are at work. Increased long-term migration is a world-wide phenomenon and is as much a concern in Australia as here. With major corporates increasingly dispersed, the labour market has become global and workers in their 20s and 30s now see working overseas as a natural step on their career path.
"People see the opportunity to climb the ladder by going overseas," says Khawaja, "and with larger firms there are more opportunities."
He says Australian firms have been actively recruiting New Zealand workers to plug skill shortages.
Bedford agrees: "We have a challenge in that Australian businesses will seek labour in New Zealand because we are one of the best sources for their businesses - just as Australia offers one of the best sources of labour for ours.
"It just so happens that we can't attract more over here because our wages - or the way they see our wages - are not as competitive.
"If a change in Government brought substantial tax cuts, I suspect it would have little impact on migration to Australia."
The occupations of those heading across the Tasman reflect demand from the booming mining sector for drivers, building tradesmen and electricians as well as Australia's expanding economy - specialised managers, primary teachers, nurses, sales and service workers.
But, the experts stress, people move for more than economic reasons. With so many New Zealanders living across the Tasman, many go to join family - there's a critical mass effect.
There is the attraction of bigger, cosmopolitan cities with livelier arts scenes and night life. Warmer weather may be one reason why more NZ migrants now head for Queensland than Sydney and Melbourne.
They choose Australia rather than another country because it's easy, close and familiar, says Graeme Hugo: "People really don't miss a beat if they skip across the Tasman, almost everything in daily life is quite similar. There's a lot of overlap in the media and what's on TV.
"New Zealanders tend to hit the ground running. They don't experience language and cultural difficulties, or the covert discrimination that goes on in the labour market. Their qualifications are recognised."
With no official barriers to transtasman migration, Hugo and Bedford say the flow is more typical of an internal migration.
"A lot of talented people are going over the Tasman for the same reason people go from Taumarunui or Otorohanga to Auckland or Wellington," says Bedford. "It's where the good jobs are."
He has retired colleagues who have homes in both countries and divide their time between them equally.
"We have to accept New Zealanders aren't going to be stuck permanently in New Zealand or permanently in Australia, anymore than they are permanently based in Auckland or Hamilton and not moving backwards and forwards."
The increase in departures is part of an international trend, although New Zealand is more exposed than other countries because it has a bigger neighbour next door with no immigration restriction and an economy benefitting from a mineral boom.
The outflow will dwindle when Australia's economic expansion stalls - the cycle has an inverse link with Australia's unemployment rate, says the Labour Dept.
Meanwhile, says Bedford: "The only way we're going to stop the labour going to Australia is to request the Australian government to stop New Zealanders having [automatic] access to Australia - and that's not going to happen."
