Quality Statement

Label
Iwi affiliation - 2023 Census: Information by concept en-NZ
Definition

An iwi (a Māori tribe) is one of the largest kinship groupings and is generally made up of several hapū that are all descended from a common ancestor. Hapū are clusters of whānau (families) where the whānau is usually an extended family grouping consisting of children, parents, often grandparents, and other closely related kin.

For statistical purposes, Stats NZ defines iwi as a whakapapa-based kinship grouping that generally has several hapū, one or more active marae, and a recognised structure that represents the interests of the iwi, such as a rōpū whakahaere, committee, or board.

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Overall quality rating

Moderate quality
Data quality processes section below has more detail on the rating.

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Priority level

Priority level 1
A priority level is assigned to all census concepts: priority 1, 2, or 3 (with 1 being highest and 3 being the lowest priority).
Iwi affiliation is a priority 1 concept. Priority 1 concepts are core census concepts that have the highest priority in terms of quality, time, and resources across all phases of a census.
For the 2018 Census, iwi affiliation was priority level 2. For the 2023 Census, the priority level was increased to level 1 to reflect the importance of iwi affiliation information.
The 2023 Census: Final content report has more information on priority ratings for census concepts.

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Subject population

Māori descent census usually resident population count
‘Subject population’ means the people, families, households, or dwellings that the variable applies to.

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How this data is classified

Iwi affiliation uses a 2-level hierarchical classification.

Census iwi and iwi-related groups V2.1.0 has more detail for examining the classification.

Level 1 of the classification lists 18 broad categories. These include:

  • 12 categories that group iwi into geographical regions for statistical purposes
  • a category for confederations and waka, where the iwi is not named
  • a category for when iwi are named but the region is not known
  • a category for when hapū are affiliated to more than one iwi
  • a category for when the region is known but the iwi is not named
  • a category for people who ‘Don’t know’ their iwi
  • a category for ‘Not elsewhere included’ categories.

Level 2 of the classification lists iwi and iwi-related categories:

  • within the 12 geographical regions there are 139 iwi categories
  • within the four level 1 categories for ‘Confederations and waka’, ‘iwi named, region not known’, ‘Hapū affiliated to more than one iwi’, and ‘Region known, iwi not named’ there are a total of 45 ‘Partially coded iwi’ categories
  • there is a category for ‘Don’t know’
  • the ‘Not elsewhere included’ category contains the residual categories ‘Refused to answer’, ‘Response unidentifiable’, ‘Response outside scope’, and ‘Not stated’.

Iwi affiliation is a multiple-response variable, so the total number of responses will be greater than the number of respondents.

Data is only published at level 2 of the classification. The geographic regions provide structure to the long list of iwi and are not intended for reporting purposes.

Census Iwi grouping recode V2.1.0 can be used to publish data with iwi grouped together.

Thirty-six new categories were added to level 2 of the classification between 2013 and 2018. A further nine categories were added to level 2 of the classification between 2018 and 2023.

Data sources and methodology for iwi affiliation in the 2023 Census provides more detailed explanations about how the classification has changed over time.

Standards and classifications has more information on what classifications are, how they are reviewed, where they are stored, and how to provide feedback on them.

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Question format

Iwi affiliation data is collected from the individual form (question 13 paper form). On both the paper and online forms, those who respond that they are of Māori descent or responded that they don’t know if they are of Māori descent were routed to the iwi question.

There have been changes to the question wording that have resulted in differences in wording, layout, and the way a person could respond on the online and paper forms.

Online and paper form changes:

  • The question asked respondents to specify the ‘Region(s)/rohe’ of their iwi. In 2018, the question asked respondents to specify the ‘Region(s)’ of their iwi.

Online form changes:

  • Stats NZ worked with Te Kāhui Raraunga Charitable Trust (TKR) to redesign the iwi affiliation question in the online form. The online form presented a map of New Zealand so respondents could select a region and then select their iwi from a list of iwi in that region. Respondents could bypass the map to select from a list of iwi. Respondents could also choose to manually type the name of their iwi into a text box. The text box in the iwi affiliation question had as-you-type (AYT) functionality, which included the 139 iwi from the classification. In 2018, the AYT list had almost 300 options, which included synonyms and spelling variations.
  • Respondents could select up to 16 iwi. In 2018, the iwi affiliation question in the online form allowed respondents to select up to five iwi.

Paper form changes:

  • Respondents had space to write five iwi on the paper form (in 2018, respondents had space to write four iwi).
  • In 2023, the routing question, ‘Do you know the name(s) of your iwi (tribe or tribes)?’ was incorporated into the iwi question rather than being a separate question on the form.

Design of forms for the 2023 Census (page 80) provides a description of the design and functionality of the iwi affiliation question in the 2023 Census, as well as rationale for the changes.

Stats NZ Store House has samples for both the individual and dwelling paper forms.

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Examples of how this data is used

Te Whata – a data platform tailored specifically by iwi for iwi – is where Te Kāhui Raraunga (TKR) will be publishing Māori descent and iwi affiliation data.

Data-use outside Stats NZ:

  • monitor the performance of Te Tiriti o Waitangi/Treaty of Waitangi obligations by the Crown and iwi
  • support the allocation of resources and funds to and within iwi
  • help with Waitangi Tribunal decisions, for example, on land ownership and fishing rights
  • help iwi organisations, local and central government agencies, and non-governmental organisations to evaluate, plan, and provide services to iwi in areas such as housing, health, and education.
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Data sources

Alternative data sources were used for missing and residual census responses and responses that could not be classified or did not provide the type of information asked for. The table below shows the distribution of data sources for iwi affiliation data.

Data sources for iwi affiliation data, as a percentage of Māori descent census usually resident population count, 2023 Census
Source of iwi affiliation data Percent
2023 Census response 73.2
Parental data from 2023 Census response 12.1
Historical census response 8.5
Parental data from historical census response 1.7
Admin data 1.9
Parental data from admin data 0.2
No information 2.5
Total 100.0
Note: Due to rounding, individual figures may not always sum to the stated total(s).

Alternative data sources for iwi affiliation were introduced for the first time in the 2023 Census.

Historical census responses from the 2018 and 2013 Censuses were combined together.

The following admin data sources were used, in this priority order:
  • Ministry of Education tertiary data and Ministry of Social Development student loans and allowances data (combined together)
  • Ministry of Education schools data.

Parental responses from 2023 Census responses, historical census responses, and admin data were also used where parental relationships were found in Department of Internal Affairs data.

Data sources and methodology for iwi affiliation in the 2023 Census provides more detailed explanations about the data sources for iwi affiliation in the 2023 Census.

Editing, data sourcing, and imputation in the 2023 Census describes how data quality is improved by editing, and how missing and residual responses are filled with alternative data sources (admin data and historical census responses) and statistical imputation. This webpage also contains a spreadsheet that provides additional detail on the admin data sources.

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Missing and residual responses

Missing and residual responses represent data gaps where respondents either did not provide answers (missing responses) or provided answers that were not valid (residual responses).

Where possible, alternative data sources have been used to fill missing and residual responses in the 2023 Census.

Percentage of iwi affiliation ‘Not stated’ for the Māori descent census usually resident population count:

  • 2023: 2.5 percent
  • 2018: 28.7 percent
  • 2013: 3.1 percent

For output purposes, the residual category responses are grouped with ‘Not stated’ and are classified as ‘Not elsewhere included’.

Percentage of iwi affiliation ‘Not elsewhere included’ for the Māori descent census usually resident population count:

  • 2023: 2.5 percent
  • 2018: 29.3 percent
  • 2013: 3.3 percent
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Data quality processes

Overall quality rating: Moderate
Data has been evaluated to assess whether it meets quality standards and is suitable for use.

Three quality metrics contribute to the overall quality rating:

  • data sources and coverage
  • consistency and coherence
  • accuracy of responses.

The lowest rated metric determines the overall quality rating.

Data quality assurance in the 2023 Census provides more information on the quality rating scale.

Data sources and coverage: Moderate quality
The quality of all the data sources that contribute to the output for the variable were assessed. To calculate the data sources and coverage quality score for a variable, each data source is rated and multiplied by the proportion it contributes to the total output.

The rating for a valid census response is defined as 1.00. Ratings for other sources are the best estimates available of their quality relative to a census response. Each source that contributes to the output for that variable is then multiplied by the proportion it contributes to the total output. The total score then determines the metric rating according to the following range:

  • 0.98–1.00 = very high
  • 0.95–<0.98 = high
  • 0.90–<0.95 = moderate
  • 0.75–<0.90 = poor
  • <0.75 = very poor.

While alternative data sources are now being used to fill in some missing and residual responses, the accuracy ratings of those sources are relatively low, and there is still a proportion of people with no iwi affiliation data. This resulted in a score of 0.90, leading to the quality rating of moderate.

Data sources and coverage rating calculation for iwi affiliation data, Māori descent census usually resident population count, 2023 Census
Source of iwi affiliation data data Rating Percent Score contribution
2023 Census response 1.00 73.21 0.73
Parental data from 2023 Census response 0.73 12.07 0.09
Historical census response 0.68 8.52 0.06
Parental data from historical census response 0.47 1.67 0.01
Admin data 0.56 1.88 0.01
Parental data from admin data 0.37 0.18 <0.01
No information 0.00 2.47 0.00
Total 100.00 0.90
Note: Due to rounding, individual figures may not always sum to stated total(s) or score contributions.

Consistency and coherence: Moderate quality
Iwi affiliation data is mostly consistent with expectations across consistency checks. There is an overall difference in the data compared with expectations and benchmarks, which can be explained through a combination of real-world change, incorporation of other sources of data, or a change in how the variable has been collected.

Iwi counts are higher, sometimes considerably higher, than previous censuses. A number of factors have contributed to this such as changes in how the variable has been collected, the incorporation of alternative sources of data, improvements in response rates for Māori in the 2023 Census, more people with multiple iwi affiliations, and potentially an increased awareness of whakapapa.

Changing the way respondents could answer the question has had an impact on the data. Rather than asking respondents to write their iwi, online respondents were encouraged to choose from a list of iwi. This list only contained the names of the 139 iwi in the classification; partially coded categories were intentionally not included in the list. Presenting a list of iwi can help people respond accurately and select multiple iwi. However, it may also shape the way people respond. In some instances, the counts for individual iwi have changed from previous censuses, which may be a consequence of this change.

As this was the first time this methodology has been used, a conservative approach was taken in applying the rating for metric 2. If alternative data sources are used in future collections, additional data points will give greater confidence in the observed trends.

Accuracy of responses: High quality
Iwi affiliation data has only minor data quality issues. The quality of coding and responses within classification categories is high. Any issues with the variable appear in a low number of cases (typically in the low hundreds).

The text-coding accuracy is considered high because:

  • most online respondents selected their iwi using the map or as-you-type (AYT) list, which meant there were fewer free-typed responses compared with previous censuses
  • a team of people with specialist knowledge of te reo Māori and iwi were employed to ensure the free-typed responses were coded accurately.

Improvements were also made to the iwi question in the online form, which has resulted in better quality data. For example, a map of New Zealand was introduced to make it easier for respondents to select their iwi.

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Recommendations for use and further information

When using this data users should be aware of the following:

  • The design of the 2023 Census online form may have impacted the way respondents have responded to the iwi affiliation question for ‘Tainui Awhiro’, ‘Waikato’, and ‘Tainui, iwi not named’. The proportion of online respondents saying they affiliate with ‘0312 Tainui Awhiro’ was high, while the proportion of online respondents saying they affiliate with ‘0304 Waikato’ and ‘2001 Tainui, iwi not named’ was much lower than previous censuses. The ‘0312 Tainui Awhiro’ category was added to the classification for 2023 and was therefore available as one of the listed iwi to select. In the past, people who said they affiliate with ‘Tainui Awhiro’ would have been coded to ‘0304 Waikato’. Also, in the past many people said they affiliate with ‘Tainui’ (which would have been coded to ‘2001 Tainui, iwi not named’) or ‘Tainui Waikato’ (which would have been coded to ‘0304 Waikato’).
  • Iwi recently added to the classification are not found in the admin data from the Ministry of Education and the Ministry of Social Development. This is because the data was collected using older versions of the iwi classification. Data sources and methodology for iwi affiliation in the 2023 Census explains how this was taken into account when determining the order in which the alternative data sources were used. This is because there is a risk these iwi could be undercounted.
  • Because the online map and as-you-type lists (AYT) did not present any iwi-related categories (for example, the ‘Confederations and waka’, ‘iwi named, region not known’, ‘Hapū are affiliated to more than one iwi’, or ‘Region known, iwi not named’ categories), fewer people provided these types of responses in the 2023 Census. However, some people who did not answer the iwi affiliation question were coded to these categories using the alternative data sources. In particular, ‘2004 Aotea, iwi not named’ has seen a large increase in its count because of the use of admin data.
  • ‘Don’t know’ responses are less likely to be found in admin data. Because of this, the number of people who don’t know their iwi may be undercounted.
  • Iwi affiliation data from the 2018 Census is not suitable for providing an official iwi count. Published timeseries data will only include iwi data for the 2013 and 2023 Censuses.

Comparing with 2013 Census
The 2023 Census data can be compared with the data from the 2013 Census. However, users should be aware of the following changes to the 2023 Census methodology:

  • Alternative data sources have been used to fill in all missing Māori descent data, which increases the Māori descent census usually resident population count, and the subject population for iwi affiliation.
  • Alternative data sources have been used to fill in missing iwi affiliation data where possible. People whose iwi data came from an alternative source tended to affiliate with more iwi on average.
  • The maximum number of iwi per person was 16, whereas in 2013 the maximum number was five.

When making comparisons with counts from the 2013 Census (or earlier), residuals should be included so changes in the use of alternative data sources are clear. When comparing percentages, the ‘Total stated’ population should be used as the denominator.

Comparing with 2018 iwi estimates
To reduce the negative impact of not releasing official iwi counts from the 2018 Census, Stats NZ and technicians of the Data Iwi Leaders Group (ILG) worked together to produce 2018 iwi estimates. Users should be aware of the differences in methods:

  • The 2018 iwi estimates used alternative data sources and weightings to increase counts for each iwi so that in effect there would be no one in the subject population with a residual code.
  • In 2023, alternative data sources were used to fill in missing iwi data. However, there are still some people in the subject population with a residual code.
  • In 2023, the maximum number of iwi per person was 16, whereas in 2018 the maximum number was five.

When making comparisons with counts from 2018 iwi estimates, residuals should be included so changes in the use of alternative data sources are clear. When comparing percentages, the ‘Total stated’ population should be used as the denominator.

Comparisons with other data sources
There are currently no other publicly available counts of people who affiliate with all iwi.

However, there are surveys and sources other than the census that collect iwi affiliation data. Data users who have access to these sources are advised to familiarise themselves with the strengths and limitations of the sources before use. The census aims to be a national count of all individuals with Māori descent, while the other surveys are only based upon a sample of the population.

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Information by variables from previous censuses

To assess how this concept aligns with the variables from the previous census, as well as the iwi affiliation estimated counts used in 2018, use the links below:

Contact our Information centre for further information about using this concept.

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Information

History

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Revision Date Responsibility Rationale
35 26/09/2024 10:00:57 AM