Painting a picture of trans-Tasman mortality

The determinants of health and mortality inequalities in New Zealand and Australia have been subjected to research, with the influence of a range of socio-economic and demographic influences (deprivation, social class, ethnicity) receiving notable attention. Both countries are considered privileged, positioned amongst the world leaders in rankings of mortality and life expectancy. This paper reports on observed rates of mortality and views how the countries have fared over time with respect to one another.

This study derives comparable rates of mortality for both New Zealand and Australia, disaggregated by age and sex for the time period 1948-2008. The age-standardised rates are visualised using the Lexis mapping software program, showing the relative differences between the countries over time whilst simultaneously highlighting age, period and cohort effects.

Relative to Australia, New Zealand had advantageous rates of mortality across almost all age groups between the years 1948 and 1980 (approximately). For both sexes, a dramatic reversal of fortunes in New Zealand has followed relative to Australia. For example, for younger males in New Zealand, the reversal is startling. Over the time period observed, males aged 10-20 years in New Zealand have moved from an advantageous position of having a mortality rate 20% lower than Australia to a relative position of 50% higher.

The social and economic forces in both New Zealand and Australia which may have driven the divergence require further scrutiny. It is argued here, that the changing fortunes of the populations are linked to the process of selective migration and the large-scale population movements between the countries facilitated by the Trans-Tasman Travel Arrangement. These findings have important implications for policy formation and service planning, if the inequality in mortality between the areas of study is to be addressed.