We still don't count: the under-counting and under-representation of Māori in health and disability sector data.

Aim: To examine ethnicity data quality; in particular, the representation and potential under-counting of Māori in health and disability sector data, as well as implications for inequities.

Methods: Māori and non-Māori ethnicity data are analysed at: 1) a population aggregate level across multiple 2018 datasets (Estimated Resident Population, Census Usually Resident Population, Health Service User (HSU) population and Primary Health Organisation (PHO) enrolments); and 2) an individual level for those linked in PHO and 2018 Census datasets. Ethnicity is drawn from the National Health Index (NHI) in health datasets and variations by age and gender are explored.

Results: Aggregate analyses show that Māori are considerably under-represented in HSU and PHO data. In linked analysis Māori were under-counted on the NHI by 16%. Under-representation in data and under-counting occur across both genders but are more pronounced for Māori men with variations by age.

Conclusion: High quality ethnicity data are fundamental for understanding and monitoring Māori health and health inequities as well as in the provision of targeted services and interventions that are responsive to Māori aspirations and needs. The continued under-counting of Māori in health and disability sector data is a breach of Te Tiriti o Waitangi and must be addressed with urgency.