This post describes where researchers can find information about Māori descent in the datasets within the IDI.


There are two different Māori identification variables within New Zealand’s official statistics – Māori ethnicity and Māori descent. Ethnicity and descent are two different concepts, with different theoretical foundations, legislative requirements, data sources as well as different applications by researchers, policy makers and Māori organisations. Both Māori identification measures require the respondent to be willing to identify as Māori in the context that the data is gathered.

Ethnicity is a measure of self-reported cultural affiliation with an ethnic group (see: and is commonly used in social and health research to classify individuals or populations.1 A previous VHIN post provides more details about the ethnicity data in the IDI (see here

Māori descent is based on biological ancestry and genealogy using definitions that are defined in legislation. Both the 1993 Electoral Act and the 1974 Māori Affairs Act (Te Ture Whenua Māori) state “‘Māori’ means a person of the Māori race of New Zealand; and includes any descendant of such a person”.2 Māori descent is used to determine both the Māori descent population (people who identify as being descended from Māori) and the Māori electoral population. The former includes only those who answer yes or āe to the Māori descent question. The Māori electoral population includes the same people plus a proportion of those who did not respond or responded no or kāore based upon imputation from their other responses within the Census  (e.g. island, iwi, Māori ethnicity, and descent composition of the rest of the household, and age group) .3

There is increasing interest in the use of Māori descent in describing and analysing individual and collective outcomes for Māori. The primary reason for this is that it aligns with Māori concept of identity based on whakapapa, which is the fundamental principle of Māori identity and the basis of iwi affiliation as well as iwi registration. In the 2013 Census, just over 16% of Māori who identified as being of Māori descent did not identify ethnically as Māori. So the Māori descent population is larger than the Māori ethnic population and has a slightly different age structure (slightly older), which can impact on rates of population outcomes when not age-standardised.

Māori descent is a better, but still far from perfect, proxy for genotype compared with the social science concept of ethnicity. Descent may be preferable in investigations of genetic or inherited pre-dispositions or conditions.

Either Māori ethnicity or descent (or both) may be used to define Māori populations, depending on the research question and the intended audience.3  For example, Te Kupenga, the post-censal survey of Māori, draws its sample from those who identify as Māori either ethnically or by descent.

Where can I find Māori descent information in the IDI?

Information about Māori descent is available from two different government sources in the IDI: New Zealand birth and death registrations and the Census (see Table 1). Census 2013 data is currently in the IDI and includes Māori descent. Census 2018 data is currently scheduled to be added to the IDI in December 2019 and will also include Māori descent. Ministry of Education collects iwi information but does not collect Māori descent.

Table 1 Data sources in the IDI March 2019 refresh with Māori descent information, the specific questions and response categories

Data sourceMāori descent questionResponse categories
2013 NZ Census of Population and Dwellings“Are you descended from a Māori (that is, did you have a Māori birth parent, grandparent or great-grandparent, etc)?”Yes, No, Don’t know
NZ birth registrations (from September 1995)“Is this child/person the descendant of a New Zealand Māori?”

“Is the mother/father the descendant of a New Zealand Māori?”
Yes, No, Not sure
NZ death registrations (from September 1995)“Was the deceased descended from a New Zealand Māori?”Yes, No, Don’t know

For the 2013 Census, the Māori descent question was a filter question for the iwi affiliation. This meant that only those who answered yes/āe to the Māori descent question were asked to complete the iwi affiliation questions. This changed in 2018, with those who answered either yes/ āe or don’t know/aua being directed to the iwi affiliation question. The Census 2018 Māori descent population also differs from the Census 2013 in the data sources and methods used to construct the population. The Census 2018 Māori undercount required the implementation of data linkage with non-Census data sources in order to construct the Māori descent population and resulted in a higher proportion of the national population being of Māori descent compared with Census 2013 results. This change of approach and the difference in the counts mean that Census 2018 counts and calculations derived from them may not be comparable with counts and calculation based on previous Census Māori descent populations.

The Census questions about Māori descent are as follows

On the English language Individual Census form

Are you descended from a Māori (that is, did you have a Māori birth parent, grandparent or great-grandparent, etc)?

The response categories are yes, no, don’t know.

On the Te Reo Māori language Individual Census form

He tūpuna Māori ōu?

The response categories are āe, kāore, aua,


The most comprehensive source of Māori descent information outside of the Census is birth and death registrations form Department of Internal Affairs (DIA). It is important to note that the method of collecting Māori descent information for New Zealand’s birth and death registrations changed in September 1995. Until 1995, death and birth registrations collected information based on the degree of Māori or Pacific Island blood of parents. If parents were not of Māori or Pacific Island descent, no details were required, and no information was collected.4  In addition, only people who indicated to have a “Māori blood quantum of half or more” were defined as being of Māori descent, thereby excluding many people who were in fact descendants of Māori, resulting in an underestimation of the Māori by descent population.5 In September 1995, the question about Māori descent on birth registrations became more closely aligned with the 1996 Census question, and asked all new parents “Is this child/person the descendant of a New Zealand Māori?”, as well as information about their own descent. NZ death registrations contain information about Māori descent for the deceased person, but prior to the September 1995 change mentioned above, collecting such information was not mandatory, resulting in a very large undercount of Māori deceased.6 Thus, Māori descent information is available within Birth, Deaths and Marriages data for births from 1995 (although coverage is much better from 1998 onwards when the collection of birth and death data was digitised).

Statistics New Zealand has investigated and compared Māori descent information in the 2013 Census and birth registrations from 1998 onwards (the year from which birth registrations were digitised) using the IDI.7 Completion of the Māori descent question on birth registrations since 1998 was high, with around 0.5% missing responses and a further 2.9% ‘not sure’. Completion of the Māori descent question in the 2013 Census is comparatively lower, with around 10% missing responses (unidentifiable response or no response stated), and a further 2% ‘don’t know’ responses.8 For birth registrations from 1998 onwards that could be linked to 2013 Census records within the IDI, a high level of 96% agreement was found between responses, i.e. children who had ‘yes’/‘no’ recorded for Māori descent on their birth record had the same response recorded in the 2013 Census.7

Together the 2013 Census and birth/death data in the IDI provide Māori descent information for a large proportion of the population including anyone born in New Zealand after 1998 (and their parents named on the birth certificate), anyone who died in New Zealand after 1998, and anyone who completed the descent question on the 2013 Census. The addition of the Census 2018 data to the IDI should result in a higher proportion of the population being ascribed Māori descent information.

Outside the IDI there are some additional sources of Māori descent information, such as the Electoral Commission. The Tūhono Trust has a legislated role as Kaitiaki (guardian) of the iwi affiliation of Māori who are registered to vote, so it is an important source of Māori descent and iwi affiliation information.


Information on Māori descent can be found in the 2013 Census and New Zealand birth and death registrations. Completeness of responses to the Māori descent question is higher for birth registrations than for the 2013 Census. When using information on Māori descent from the New Zealand birth and death registrations, researchers are recommended to only use data from 1998 onwards (when coverage is better).


  1. Statistics New Zealand. Ethnicity (link).
  2. Statistics New Zealand. Accessed 03 December, 2020.
  3. Statistics New Zealand. Imputation of Māori Descent for Electoral Calculations. Accessed 23 October, 2019.
  4. Statistics New Zealand. IDI Data Dictionary: Life event data (July 2015 edition). Wellington: Statistics New Zealand, 2015.
  5. Khawaja M, Boddington B, Didham R. Growing ethnic diversity in New Zealand and its implications for measuring differentials in fertility and mortality Wellington: Statistics New Zealand, 2007.
  6. Sporle A, Pearce N. Impact of changes in the death registration process upon Māori mortality statistics. NZ Med J 1999;112:411-2.
  7. Bycroft C, Reid G, McNally J, Gleisner F. Identifying Māori populations using administrative data: A comparison with the census. . Wellington: Statistics New Zealand, 2016.
  8. Statistics New Zealand. 2013 Census QuickStats about Māori. Wellington: Statistics New Zealand, 2013.

By Andrew Sporle, Frederieke Petrović-van der Deen, Sheree Gibb

Originally published 12 November 2019.