WELLINGTON, May 14 (Xinhua) -- Migrant arrivals were provisionally estimated at 152,200 and migrant departures at 96,100 in the 12 months ended March 2019, Stats NZ said on Tuesday. This resulted in a provisional estimate of annual net migration of 56,100.

"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."

With each extra month of data, the migration estimation model has more information about the border crossings it is trying to estimate.

"When the October estimates were first published in January 2019, only 88 percent of border crossings were definitively classified," Theyers said.

"Now, in May 2019, 98 percent can be classified and only 2 percent needs to be modelled," Theyers said.