In December there was a net loss of 3100 migrants to Australia, Statistics NZ said, up from 2000 in December 2010.
Last year recorded the highest ever net loss of people to Australia, departures outstripping arrivals nearly four to one.
The Labour Department points out, however, that while more New Zealanders left for Australia in the latest cycle (2004 to 2010) than in the one before (1997 to 2003) the number leaving for countries other than Australia was 84 per cent lower.
"The net effect is that fewer New Zealanders departed the country between 2004 and 2010 than over the seven years 1997 to 2003."
And relative to the size of the population transtasman departures are lower now than they were in the late 1970s, it said. The cumulative effect, however, is that around 500,000 New Zealanders live in Australia out of a total diaspora estimated between 700,000 and 1 million, while one in five New Zealand residents were born overseas.
ASB economist Jane Turner said the net migration outflow last year had helped alleviate some of the pressure on a tight housing market, especially in Canterbury and Auckland, and was another factor reducing any urgency for the Reserve Bank to raise interest rates.
Goldman Sachs economist Philip Borkin said slowing population growth would weigh on domestic demand and growth in household consumption this year.
He expects population growth to slow to around 0.7 per cent over 2012, from an estimated 0.8 per cent last year and 1.2 in 2010.
"Once it is clear that earthquake reconstruction will begin ... the trend in Canterbury outflows will at least stabilise," he said. "Furthermore, with the Australian labour market also showing signs of slowing, this may also slow the number leaving to cross the Tasman, although this requires an ongoing improvement in the New Zealand market."
