The population gain from migration has climbed to a 1-year high as the net loss of people to Australia dwindled to just 210 last month, the lowest for at least 18 years.
The net inflow of permanent and long-term migrants was 4100 in April, seasonally adjusted, the second-highest monthly tally on record.
It pushed the annual net gain to 34,400, up from 31,900 in the year ended March.
The only time annual net migration had been higher than that was between the July 2002 and December 2003 years, peaking at 42,500 in May 2003, Statistics New Zealand said.
Just two years ago, in the year to April 2012, there was a net migration loss of 4000.
Nearly two-thirds of the turnaround since then has been in the net flow of New Zealand citizens to Australia, from a net loss of 39,600 two years ago to a loss of 14,800 in the latest April year.
Offsetting that was a net gain of 48,700 non-New Zealand citizens in the latest year, up 13,100 from two years ago. The three main source countries were India (6400), China (6200) and the United Kingdom (5900). Westpac economist Felix Delbruck said the monthly trend suggested annual net migration was set to surpass 40,000 by the end of the year.
"The bulk of the lift in net migration over the past year has reflected transtasman movements, due to the unusual fact that New Zealand's job market is improving while Australia's is still soft," he said.
However, the current migration boom would not last forever, Delbruck said.
"We expect the Australian economy to strengthen further by next year, and the New Zealand economy to slow in the second half of the decade as the Canterbury rebuild enters its let-down phase. When that happens net migration could see quite a sharp reversal."