'Significant' milestone: NZ's population hits 5 million

New Zealand's resident population has now reached 5 million.

Stats NZ announced today that we cracked the milestone in March.

It took just 17 years to add one million people after hitting 4 million in 2003. About half that million came from natural increase (births minus deaths) with the other half coming from net migration.

On average, the population has grown by 1.8 per cent a year since 2013, driven by net migration.

It took just 17 years to hit 5 million - New Zealand's fastest million ever. Image / Stats NZ

Although it was still a provisional milestone, hitting 5 million was a "significant event" for New Zealand, Stats NZ's population insights senior manager Brooke Theyers said.

The Covid-19 pandemic had caused unusual international travel and migration patterns in recent months, which had boosted net migration as more Kiwis arrived home from overseas, she said.

"At the same time, New Zealand citizens may have been unable or reluctant to head offshore."

Population estimates will need to be revised to incorporate all 2018 Census data, which will happen later this year. International migration estimates will also need revision - especially if recent migrant arrivals head back overseas when border restrictions are relaxed and travel resumes.

Stats NZ conceded they couldn't tell whether our 5 millionth person was a new migrant who arrived in New Zealand on a plane, or if it was a newborn baby. The precise date when we hit 5 million also isn't available yet.

But it's estimated that at March 31 had a resident population of 5,002,100, Stats NZ said.

Net migration has been boosted by the Covid-19 pandemic as Kiwis return home, but may need revising when travel resumes as people may leave the country again, Stats NZ said.

Where's the growth happening?

According to previous statistics Northland is the fastest-growing region in the country, with more than 27,000 more people living in the region than five years ago.

Latest Census figures from 2018 released by Stats New Zealand show Northland registered an 18.1 per cent growth between 2013 and 2018 to sit at 179,076, followed by Bay of Plenty (15.2 per cent), and Waikato (13.5 per cent).

The West Coast was the only region where population declined, down 1.8 per cent to 31,575.

Mangawhai rural recorded the largest population growth of 702 over that period, followed by 633 at Waipū, and 537 at Kaiwaka.

Northland councils have made provisions in their policy documents to cater for expected population rise that will put more pressure on existing infrastructure and demand for housing.

Whangārei District Council chief executive Rob Forlong said the latest stats was a good result and was well within the council's projections.

He said Marsden Point and Ruakākā's population was now approaching that of Kaikohe, and that Tikipunga, Maunu and Three Mile Bush areas were also growing rapidly.

"WDC has been planning for the population increase for many years. The population increase is requiring more infrastructure, and we have responded by lifting our annual capital budget from $49m six years ago to $85m last year.

"Examples of new infrastructure include the new water treatment plant being built in Whangārei, new cycleways, roading improvements and seal extensions, and amenity projects like playgrounds, the ongoing developments around the Hatea Loop and on Pohe Island," he said in September.