New Zealand will have more than five million people by 2031 - with almost 2 million living in Auckland, according to Statistics New Zealand projections.
New subnational population projections show Auckland will continue to be New Zealand's fastest growing region, and account for three-fifths of the country's population growth between 2011 and 2031.
In 2031, 38 percent of Kiwis will reside in Auckland, compared to 34 percent in 2011. It is projected Auckland would have almost 2 million of New Zealand's 5.2 million people.
Natural increase (births minus deaths) is projected to account for two-thirds of Auckland's growth, and net migration (arrivals minus departures) the remaining one-third.
Of New Zealand's 16 regions, only Auckland will have more births in 2027-31 than in 2007-11, but all regions will have more deaths as the population ages.
"Auckland has a slightly younger population than other regions, and younger populations tend to have more births and relatively fewer deaths," population statistics manager Andrea Blackburn said.
Of New Zealand's 67 territorial authority areas, 44 are projected to have more people in 2031 than in 2011. However, population growth rates will slow over the period for all areas because of the contrasting trends between births and deaths.
The fastest growth between 2011 and 2031 is expected in Selwyn and Queenstown-Lakes districts (up an average of 1.9 percent a year).
Despite an estimated population loss of 8,900 in the year ended June 2011 following the earthquakes, Christchurch city is projected to increase by an average of 1,500 a year during 2012-16 and 2,500 a year during 2017-31.
Statistics NZ produces the growth projections every two to three years to assist planning by communities, local councils, and government.