Over the past four years net immigration has accounted for 70 per cent of population growth, dwarfing the contribution of natural increase (births minus deaths). Net immigration includes the coming and going of New Zealanders, who accounted for a quarter of the arrivals and half of the departures.
It has been driven in equal measure by two trends: a drying up of the net flow of people from New Zealand to Australia; and an increase in net immigration from the rest of the world.
On average over the past four years, there was actually a net gain — albeit just 74 people a year — in the net transtasman flow, compared with an average loss of 26,900 between 2011 and 2014 inclusive. Meanwhile, over the past four years the net inflow of migrants from the rest of the world (excluding Australia) averaged 66,100 a year, up from an average 39,700 over the four years before that.
Both of those trends show signs of turning in the latest year.
In the year ended July, the net loss of people to Australia was 1000, a turnaround from net gains of 500 the year before and 1800 the year before that. But it is still a meagre and exiguous trickle compared with the torrential outflows of the past, like the net 40,000 lost across the ditch in 2012.
The Australian economy is looking better than it was and the labour market with it. But Australia's unemployment rate is 5.3 per cent compared with New Zealand's 4.5 per cent, despite a labour force participation rate of 65.5 per cent there versus 70.1 per cent here.
The Reserve Bank of Australia expects wage growth to pick up as the jobless rate falls towards 5 per cent, but its forecasts do not see that rate occurring before 2020.
Meanwhile, housing unaffordability — measured by the ratio of median house prices to median incomes — is even higher in Sydney and Melbourne than in Auckland, according to the latest Demographia survey.
The gravitational pull of Australia may prove weaker in the near-term future than in the past.
And a series of policy changes have made Australia less Kiwi-friendly as a migration destination. No-one would mistake Peter Dutton for the Statue of Liberty.
So the gravitational pull of Australia may prove weaker in the near-term future than in the past.
The larger factor in the latest decline in net immigration is a pickup in departures to the rest of the world. "That's actually an echo of the increase in arrivals of those on temporary work and student visas that we saw in previous years," says Westpac senior economist Satish Ranchhod.
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"While some of the people on those visas will make the jump to permanent residency, many will depart after three to four years. We expect this pattern to continue for some time."
In the latest year, 46,500 permanent and long-term arrivals were on work visas, up 2.5 per cent on the year before, while the 23,400 arrivals on student visas was a 2.9 per cent decline on the year before.
If we turn from Statistics NZ's data on the flow of migrants, to MBIE's figures for the stock of people in New Zealand on temporary visas, we find that as of June last year, the 152,400 people here on work visas represented a 16 per cent increase on a year earlier. It has increased at a compound annual growth rate of 8.5 per cent between 2010 and 2017.
Of the 152,000, 36,700 — about one in four — were in the essential skills category, up 17 per cent on the year before. The rest were mainly family, working holidaymakers or ex-students in the study-to-work stream.
However, of the 36,700 people with essential skills visas, only 29 per cent were first-time visa holders as opposed to workers already here whose visas were renewed. That was marginally more than the 26 per cent in 2016 and 27 per cent in 2015.
And of the essential skills visas granted in 2016/17, only 3774 were in the construction trades, broadly defined to include builder's labourers and scaffolders.
If they were typical of essential skills visa holders generally, that would represent a marginal net increase of around 1100 construction workers, in a year when net immigration added 72,300 to the population needing to be housed. The previous year's numbers tell a similar story. It is hard to escape the conclusion that in the case of the housing market and building industry at least, immigration has been boosting demand a lot more than the supply side.
So while it is encouraging, from the standpoint of the country's potential growth rate, that the composition of the net inflow of migrants has been shifting towards more on work visas and fewer students, the record on the construction workforce suggests the Government needs to get a wriggle on with its proposed KiwiBuild visas.
What should we make of the forecasts of the Reserve Bank and market economists that the net migration tide will continue to ebb? The Reserve Bank, for example, expects the net inflow of working-age migrants to halve to 30,000 over the next three years.
Forecasters underestimated the strength of the upsurge and, for similar reasons, might now be overestimating the decline ahead.
Employers may well face increased competition out of Australia for Kiwi workers, but it is premature to conclude that it will quickly return to the haemorrhagic rates of the past.
And while the composition of the net inflow of migrants from the rest of the world is increasingly weighted towards workers, past visa issuance numbers suggest the system is not yet fit for purpose.
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