Māori people in New Zealand who are registered with their Iwi

People of Māori descent: have a Māori birth parent, grandparent, or great-grandparent.
People of Māori ethnicity: people who identify as Māori or feel they belong to this ethnic group. Ethnicity is a measure of cultural affiliation, as opposed to race, ancestry, nationality or citizenship. Ethnicity is self-perceived and people can belong to more than one ethnic group.

These are the final figures released by Stats NZ on 9 November 2020.

https://www.stats.govt.nz/methods/differences-between-te-kupenga-2013-and-2018-surveys

Lower-than-expected response rates in the 2018 Census, particularly for Māori, means there was considerable under-coverage in the sample frame. This raised concerns about how well the sample frame represents the Māori population of New Zealand as a whole, and the impact this may have had on the Te Kupenga data.
The investigation, carried out by Stats NZ into potential bias in the 2018, estimated that the coverage rate of the 2018 Te Kupenga sampling frame compared with the estimated total adult Māori population (ethnicity and/or descent) is just under 74 percent.

Te Kupenga was first run in 2013, with most of its content retained for the 2018 survey. Stats NZ made a few changes to reduce the burden on respondents or meet identified data needs. The biggest changes to Te Kupenga 2018 were an increase in sample size (from around 5,500 achieved responses in 2013 to almost 8,500 in 2018) and the inclusion of a new module on kaitiakitanga.

At URL provided, select 'Te Kupenga: 2018 (final) – English' file.

Te Kupenga is Tatauranga Aotearoa Stats NZ’s survey of Māori wellbeing.

The survey provides key statistics on four areas of Māori cultural wellbeing: wairuatanga (spirituality), tikanga (Māori customs and practices), Te reo Māori (the Māori language), and whanaungatanga (social connectedness). The survey’s content recognises practices and wellbeing outcomes that are specific to Māori culture, such as the knowledge and use of the Māori language, connection to marae, and whānau wellbeing.

Te Kupenga gives a picture of the social, cultural, and economic wellbeing of Māori in New Zealand, including information from a Māori cultural perspective.

A post-censal survey of around 8,500 people aged 15 years or older, and living in occupied private dwellings, who identify themselves as being of Māori ethnicity and / or descent, took place from June to August 2018.