Key Points:

The National Party DVD in which Opposition leader John Key stands in the middle of an empty football stadium suggests that the party intends to make the transtasman exodus of New Zealanders a major election issue. It is one of many questions that will be exercising Labour strategists in the run-up to polling day.

In raw numbers, the outflow is plainly costing this country. The latest figures, published this week, show that the number of New Zealanders leaving this country to live in Australia continues its remorseless rise: in net figures - we need to remember that one Australian comes here for every three Kiwis who head west - nearly 30,000 permanent and long-term migrants left this country for Australia in the year to March, compared to just over 23,000 in the previous year.

A breakdown of the numbers makes the picture slightly less bleak. Our immigration restrictions being what they are, migrants from the rest of the world are on average more skilled and/or professional than emigrants, somewhat softening the impact of the skill outflows.

Not all the occupational groups most strongly represented in the outflow are those that spring to mind when phrases like "brain drain" are bandied about: middle managers, restaurant staff and labourers are among the larger groups. But skilled tradespeople are distressingly numerous, as are nurses, teachers and - as the war of words leading up to last week's strike reminded us - young doctors.

National's right to point to the increase in the figures is not unqualified: Key may like to remind himself that when National took office in 1990 it inherited an almost-unheard-of transtasman net migration gain of 1200 which it managed to turn into a loss of almost 25,000 by the time it lost the Treasury benches to Labour at the end of the decade. The worst year ever was to March 2001, arguably as attributable to National as to Labour. And he might like to specify what precisely a National-led Government would do to turn the tide: as a former currency trader, he knows better than anyone that this country's fortunes are, to a large extent, a hostage to developments in the global economy.

And we all need to remember that New Zealanders are by nature migratory. By far the largest group of those heading to live long-term in Australia are in their early 20s, a time of life when the world beckons. Axiomatically, about one in five New Zealanders lives abroad - and the bulk of those select Australia because resettlement there involves less expense, cultural adjustment and red tape than going elsewhere.

Seen in that light, the outflows do not necessarily justify the alarm Key and others seek to generate. But in areas such as health and education the problem must be addressed.

When tertiary education is part of a market economy, graduate behaviour will be dictated by market forces. Yesteryear's doctors, who paid no fees, graduated owing the country a moral and economic debt, so a system that bonded them seemed fair; those who pay $100,000 to get a medical degree feel no such obligation. But if they cannot be chained by force of law, they might be restrained by golden shackles. Graduates in key professions who stay here for, say, 10 years - even less if they work in areas of greatest need - could have student loans written off and repayments reimbursed.

Meanwhile, and in the longer term, the question needs to be considered as part of the wider issue of Australasian economic union. If the economic grass looks greener on the other side of the fence, we cannot continue to be surprised when people with much to offer this country make the short simple leap over to that one.