Emigrants outnumbered immigrants by 100 in the year ended October, the first annual net outflow for 10 years.
There was a net outflow of 650 permanent and long-term migrants, seasonally adjusted, last month.
For seven of the eight months since the February earthquake in Christchurch the net flow has been negative.
Since the earthquake 6000 Christchurch people have left not just the city but the country, 2300 more than in the same period last year, while the inflow of migrants to Christchurch at 3200 is down 1100.
"Given the continued delays with reconstruction, insurance market gridlocks and ongoing aftershocks, it is quite likely that this theme continues," Goldman Sachs economist Philip Borkin said.