Decades of disparity: widening ethnic mortality gaps from 1980 to 1999

Maori and Pacific deaths were severely undercounted in the mid-1980s and first half of 1990s, resulting in numerator-denominator bias when calculating mortality rates by ethnicity. We used the New Zealand Census-Mortality Study to adjust for this bias and calculate corrected ethnic-specific mortality rates from 1980 to 1999.

Age-specific adjusters were calculated for the period 1980-99. They were applied to mortality data to obtain a corrected number of deaths. Mortality rates (by age and gender) were calculated by dividing the total number of adjusted deaths by the respective census counts.

Contrary to unadjusted rates, corrected Maori and Pacific mortality rates were clearly higher than non- Maori non-Pacific rates during the 1980s and early 1990s. From 1980-84 (1361 per 100,000 for males and 965 per 100,000 for females) to 1996-99 (1258 and 894), there was only a modest decrease in Maori 1 to 74 year old mortality rates. Pacific mortality rates changed little from 1980-84 (1264 and 672) to 1996-99 (1144 and 696 per 100,000 for males and females respectively). Non-Maori non-Pacific mortality rates, however, decreased by about 30% from 1980-84 (919 and 553) to 1996-99 (641 and 407 per 100,000 for males and females, respectively). Cancer (lung, prostate, breast, colorectal) mortality rates tended to increase over time among Maori compared to steadily decreasing among non-Maori non-Pacific. Of note, Pacific colorectal cancer mortality rates have increased by about ten-fold during the 1980s and 1990s. All ethnic groups experienced falls in cardiovascular disease mortality rates, but the decreases were much greater among non-Maori non-Pacific.

The gaps between Maori and non-Maori non-Pacific mortality widened over the 1980s and 1990s mainly due to steadily declining non-Maori non-Pacific mortality rates and stagnant Maori mortality rates. Likewise, the gaps between Pacific and non-Maori non-Pacific mortality also widened during that period.