A third of children in New Zealand may identify as Māori in the 2040s, a new future population study has revealed.

And the Statistics New Zealand report has projected the "European or other" ethnicity will be the only group to decrease its share of the population by 2043.

The report released today takes into account the different age structures, birth and death rates, and patterns of migration between ethnic populations.

Report lead Rebekah Hennessey said Māori and Pasifika families had younger age structures and higher fertility rates.

"This combination means future Māori and Pacific population sizes will likely continue to have a younger age structure, and with higher relative fertility rates result in more births."

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.

"Ethnic population changes at the youngest ages are a glimpse of how New Zealand's population will look in the future."

The projected increase of the Māori population accompanied a growing reconnection to Aotearoa's indigenous culture, language and identity.

Surveys in the 1970s showed there were 64,000 fluent speakers of te reo Māori, out of a population then of 400,000. Of these, only 170 children were fluent.

Whereas today, more than one in six Māori can understand and speak at a basic level or higher, reflecting the emergence of Māori immersion teaching and learning environments over the past few decades.

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 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.