But it explains only a fraction of the drop in the annual inflow of migrants; the net gain of 770 in the past year is just under half the 13,900 gain the year before, and well below the average gain of 12,000 over the past 20 years.
In the year to September, 48,800 people left for Australia (90 per cent of them Kiwis), offset by 14,700 coming the other way (63 per cent of them returning New Zealanders).
There was a net gain of 5700 from the United Kingdom, 5400 from India and 4600 from China.
ASB economist Jane Turner expects permanent departures to Australia to ease in coming months as employment growth there slows, while the labour market in New Zealand gradually recovers and skill shortages emerge, encouraging a pick-up in inward migration.
In the meantime, the weakness in net migration highlighted ongoing weakness in consumer demand and the lack of any urgency for the Reserve Bank to raise the official cash rate, she said.