Hennessey, the population estimates and projections acting manager, said: "All major ethnic group populations are projected to grow over the next two decades, although some ethnic groups are expected to grow faster than others."
She said population projections are worked out through natural increase and net migration data. A natural increase is the number of births minus deaths, and the net migration is the number of arrivals minus departures.
The projected increase of the Māori population accompanied a growing reconnection to Aotearoa's indigenous culture, language and identity.
The report shows population growth among the zero to 14-year-old Māori and Pasifika groups will be higher than other ethnicities, with Māori expected to represent a third of all children in 20 years' time.
The total Māori population was not expected to grow at the same rate, with only a marginal increase by 2043.
The difference between the percentage of under-14s and the total population is because of the higher number of Māori in younger age groups.
"Ethnic population changes at the youngest ages are a glimpse of how New Zealand's population will look in the future."
The percentage of Pasifika under-14s will also increase to 19 per cent in 20 years.
Migration rates will drive an increase in the percentage of Asian New Zealanders as well. The total Asian population is likely to be more than a million by the end of this decade, overtaking the population of Māori.
Most growth is driven by the number of people moving to Aotearoa, with birth rates having less of an effect on population growth than other groups.
A quarter of all children will belong to the "broad" Asian ethnic group in 2043, an increase from 16 per cent in 2018.
The broad "European or other" population will also grow, however the percentage make-up of the total population across all ages will marginally dip.
Of New Zealand's total population, 65 per cent will be "European or other", a decrease from 70 per cent in 2018.
People were also increasingly likely to identify with more than one ethnicity, which Hennessey said was another factor behind population growth among some groups.
"Children are more likely to have multiple ethnicities, often reflecting the different ethnicities of their mother and father."
This means ethnic group populations overlap and did not equal the total population, she said.
