New data shows the annual net migration rose in the year to March, compared to a year ago.

Annual net migration was estimated to be 56,100 for the 12 months to March 2019, up on of the 50,600 in the year to March 2018.

Estimated net migration for the year ended February 2019 was revised down to 55,100 - from 61,600.

On a monthly basis the country gained a net 4,500 permanent and long-term residents in March, down from a revised 8,565 in February but up from 3,396 in March last year.

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This suggests arrivals are easing again after a spike in the first two months of the year, although they remain at historically high levels.

"We've seen sustained high levels of net migration over the last five years," senior population insights manager Brooke Theyers said.

"Annual net migration has ranged between 48,000 and 64,000 since the year ended December 2014. The only previous time it reached these levels was over a much shorter period over 2002 to 2003."

Migrant arrivals rose up eight per cent for the year to 152,200. The largest nationality of arrivals remained returning New Zealanders.

The next largest groups by citizenship were Chinese, Indian and Australia.

A new more accurate methodology for immigration statistics has seen the figures revised since September 2018 - with new estimates for historical data.

Based on actual departures, rather that intentions filled out on arrivals cards, Statistics NZ says it will be 16 months before the data can be considered 100 per cent accurate.

However, confidence in its estimates grows with each month the new system is in place.

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Now with a fifth month of real data recorded Stats NZ demographers consider their estimates robust but have included a window of variability for each number.

They estimate that net migration figure of 56,100 could eventually vary by as much as 2.85 per cent (in either direction).