Around a third of New Zealand's population is likely to claim Asian heritage by 2048, Stats NZ says.

About 19 percent of the population claimed Asian descent in 2023, the agency says.

The projections show those identifying with Indian ethnicities are expected to increase from 7 percent of the population to about 12 percent by 2048.

Over the same period, those identifying with Chinese ethnicities are projected to increase from 6 percent to about 8 percent, the statistics show.

The projections also indicate above average growth of populations claiming Māori, Pacific, and Middle Eastern, Latin American and African (MELAA) heritage over the next two decades, which continues the demographic trends seen in recent decades.

In contrast, the number of people claiming "European or Other (including New Zealander)" heritage is projected to remain around 3.5 million.

New Zealand will become more ethnically diverse in 2048 than in 2023 due to slower population growth in the "European or Other" group in combination with high levels of natural increase and net migration for other ethnic populations, Stats NZ says.

"Our ethnic populations are changing at different rates because of a combination of different age structures, birth and death rates, and patterns of migration," said Victoria Treliving, population estimates and projections spokesperson for Stats NZ.

As a result of different growth rates, the proportion of New Zealand's population identifying with Māori ethnicity is projected to increase from 18 percent in 2023 to around 20 percent in 2048, the agency says.

Over the 25-year projection period, the Pacific ethnic proportion is likely to increase from 9 percent to around 11 percent, while the MELAA ethnic proportion is projected to increase from 2 percent to around 4 percent, Stats NZ says.

"The 'European or Other' ethnic population is the only major ethnic group projected to decrease as a proportion of New Zealand's population," Treliving said.

"This dropped from 79 percent in 2001 to 67 percent in 2023, and is projected to drop to around 52 percent in 2048."

Ethnic populations overlap because people can and do identify with multiple ethnicities, Stats NZ says.

Fifteen percent of people identified with more than one ethnicity in the 2023 Census.

This proportion is projected to grow, especially among younger people.

Each ethnic group as a proportion of the total New Zealand population varies significantly by age, according to Stats NZ.

Among those aged under 15 years, the proportions largely reflect the ethnic diversity of births, the agency says.

"About two-thirds of children identified with European ethnicities in 2023, but a growing proportion are likely to identify with other ethnicities by 2048," Treliving said.

The proportion of children claiming Asian heritage is forecast to experience the largest increase, from 20 percent in 2023 to around 34 percent in 2048.

Children identifying with Māori, Pacific and MELAA ethnicities are also expected to increase by rates ranging from 3 percent to 7 percent.

The projections also show all ethnic populations ageing.

The increase in the 65 and above share is significant for the Chinese ethnic population, from 12 percent in 2023 to around 22 percent in 2048, the projections show.

"Across all ethnic populations, this ageing is driven by lower fertility rates over time," Treliving said.

"Migration and increasing life expectancy also contribute to ageing."