Of every 100 people in New Zealand, 38 will be living in Auckland in 2031 compared with 34 in 2011, Statistics New Zealand said today.
New sub-national population projections indicate 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.
Auckland would then 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 says.
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 projection 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% a year).
Despite an estimated population loss of 8900 in the year ended June 2011, Christchurch city is projected to increase by an average of 1500 a year during 2012-16 and 2,500 a year during 2017-31.
The projections are not predictions, but an indication of the size and composition of the future population.
Statistics NZ produces low, medium, and high growth projections for every local area every two to three years to assist planning by communities, local councils, and government.