New Zealand risks becoming a "net exporter" of population in the next few months if current trends continue, economists are warning.
In November, there were 12,800 migrant arrivals and 10,600 departures, for a net migration gain of 2200 people, compared to 7100 a year earlier.
For the year to November, arrivals were down 32 percent and departures up 28 percent.
The numbers could quickly reach a point where they started to cross and more people left New Zealand than arrived, Craig Renney, policy director at the Council of Trade Unions, said.
That would hit some parts of New Zealand particularly hard, he said.
"People come to Auckland, Christchurch and so on but they leave places like Palmerston North, Ashburton. So delivering economic growth in those locations become harder.
"If you want to - Mr Luxon's phrase - go for growth, it's relatively straightforward to have economic growth if your customer base is growing 2 percent a year. But if it's shrinking it makes it harder."
Post-Christmas was a time when more people thought about leaving, Renney said.
"It may well be that in the next couple of months we end up there. We have to think about what that means for the delivery of public services. There are some that depend upon migration - medical care, teaching."
It could also be a problem because some those who left could be the higher-skilled, higher-earning people who could help growth, he said.
Infometrics chief executive Brad Olsen agreed that it was possible net migration could go negative on a month-to-month basis this year.
"Over the last six months, monthly net migration has averaged around 2336 more people coming in than leaving each month - that's much lower than through 2023, when monthly net migration averaged over 10,000 more people coming into New Zealand than leaving, and also higher than in 2017-2018 before Covid-19 impacts hit the migration figures, when monthly net migration was over 4000 per month."
There were high numbers of people leaving New Zealand, both in terms of New Zealanders looking for other opportunities and migrants who had moved here shifting away again, he said.
"Migrant arrivals are also falling back from highs, as there are simply not as many jobs available in New Zealand, and a lot of competition from workers already in New Zealand looking to get into the jobs on offer, meaning less need to bring in talent from overseas."
Rising unemployment and continued weakness in hiring would further limit inward migration, Olsen said.
"In October last year, Infometrics warned that annual net migration could turn negative in 2026/27 as migration flows shifted around again - that'd be consistent with net monthly outflows towards the end of 2025."
BNZ chief executive Mike Jones said there was a reasonable chance that migration could turn negative, although it was not his core forecast.
"The monthly net migration figures are always pretty choppy and we're currently sailing not that far above zero at a trend net inflow of about 2000 people per month. We could see that drop away a little as we head into the autumn and winter months."
He said the surge in population growth had papered over cracks in the economy for a while.
"Although it hasn't necessarily been obvious given the aggregate economic numbers stayed so weak throughout the migration boom.
"That speaks to just how soft the underbelly of the economy has been over the past couple of years, which we can now see for example by looking at GDP per capita figures.
"I think, overall, the impacts on demand from the surge in population growth were probably not as large as some expected and the supply side impacts, particularly on the labour market, have been more obvious."