Concern over quality of Māori Census data

25 July 2018
Andrew Sporle, Department of Statistics
Andrew Sporle

A researcher in the Department of Statistics is among a group of indigenous scholars sounding the alarm over the quality of Māori data in this year’s Census.

Andrew Sporle (Ngāti Apa, Rangitāne, Te Rarawa) is a founding member of Te Mana Raraunga, a high-powered group of around 100 Māori data users, analysts and IT professionals that focuses on the collection and care of indigenous data.

Andrew says that this year’s Census, the first to be run largely on-line, risks failing to deliver high quality Māori and iwi data. Full or partial information was received for around 90% of individuals this year, compared to full or partial information for 94.5% in the 2013 Census.

Statistics New Zealand is having to fill gaps using statistical methods of imputation, which means using information from other sources to determine estimated values when data is missing. Imputation improves data quality, but is less reliable than having Census responses. However, because Māori response rates to the Census are generally lower than overall rates, the Māori rate could be around 80%.

“The rate could be even lower in areas that have historically had lower coverage, such as  Northland and the East Coast,” Andrew says, “and this makes compensating for missing data a much more difficult exercise.”

The larger the proportion of the data that is missing and needs to be imputed, the bigger effect imputation will have on the net result.

“Extensive imputation will be needed to deal with missing Māori descent, Māori ethnicity and iwi affiliation data. Census 2018 may yet turn out to be the poorest-quality enumeration of Māori in recent history.”

Census data is essential for many of the functions that underpin democracy, says Andrew. It is used to project population change and inform decisions about national, regional and community services and infrastructure. It is also used to draw electoral boundaries.

“If Māori descendants are missing in large numbers from Census 2018, it could affect both the shape and number of Māori electorates,” he adds. 

High rates of Māori non-response could also compromise the quality of iwi data.

“For many iwi, the Census is the only source of reliable socio-economic and demographic data about their people.”

In addition, the Census is a major source  of Māori descent information in the Integrated Data Infrastructure (IDI), a large Government research database containing microdata about people and households.

Te Mana Raraunga is calling for an immediate and comprehensive external independent review of Census 2018 in order to understand the reasons for the lower-than-expected response rates.

Member, Professor Tahu Kukutai of Waikato University (Ngāti Tipa, Ngāti Kinohaku, Ngāti Māhanga, Te Aupōuri) says that the review needs to establish “what went wrong, where, for whom and why.” It also needs to include issues such as the impact of the digital-first policy, the Census planning process, data collection and its community engagement strategy.

Statistics New Zealand had planned to start releasing Census data in October 2018, but this has now been delayed until March next year.

Associated information

Mana Raraunga, the Māori Data Sovereignty Network, brings together some 100 Māori researchers, practitioners and entrepreneurs across the research, IT, community and non-government sectors. It advocates for Māori rights and interests in data and for the development of Māori, iwi and hapū data infrastructure and capability.

The core working group of Te Mana Raraunga is Tahu Kukutai, professor of demography at the National Institute of Demographic and Economic Analysis, University of Waikato; Maui Hudson, associate professor in the Faculty of Māori and Indigenous Studies at the University of Waikato; Andrew Sporle, Department of Statistics, the University of Auckland; Dr Donna Cormack, Department of Public Health at the University of Otago; scientist and technologist Wikuki Kingi; IT consultant Vanessa Clark; Dan Te Kanawa, Chief Executive of the Tūhono Trust; IT consultant Warren Williams; and Ngapera Riley, the deputy CEO of Figure.NZ