Identifying Māori ethnicity for estimating trends in fatal and serious non-fatal injury.

OBJECTIVES Counts of mortality and morbidity based on routinely collected national datasets have undercounted Māori, the indigenous people of New Zealand. To correct for the undercount, when estimating fatal and serious non-fatal injury incidence, the 'ever-Māori' method has been used. This study sought to determine how well the ever-Māori method corrects for the undercount. METHODS Trends in frequencies and age-standardised rates for fatal injury indicators were compared using: (a) ever-Māori classification; (b) New Zealand Census Mortality Study adjustment ratios applied to Total Māori counts from the Mortality Collection; and (c) Total Māori counts from the Mortality Collection. For serious non-fatal injury, trends using ever-Māori were compared with Total Māori from hospital discharge data. RESULTS The absolute number of injuries attributable to Māori varied depending on the method used to adjust for ethnicity status, but trends over time were comparable. CONCLUSIONS AND IMPLICATIONS At present, there is no optimal method for adjusting for the undercount of Māori in routinely collected health databases. Reassuringly, trends in fatal and serious non-fatal injury are similar across the methods of adjusting for the undercount.