Using census-mortality data from the NZ 1981–1984 (1.1 million 25- to 74-year-olds), 1996–1999 (1.5 million) and 2006–2011 (1.5 million) censuses, this study considered three research questions: (1) How much of the ethnic inequality in mortality in NZ (between Māori and Europeans) is mediated by socioeconomic factors (income, education, neighbourhood deprivation, and labour force status), and does this change over time? (2) What is the incremental increase in mediation when including smoking over and above socioeconomic position, and does this change over time? (3) What inequalities would exist if NZ had been tobacco-free between 1981 and 2011? In all three cohorts, socioeconomic factors explained 46% of male inequalities and increased over time among females from 30.4% in 1981–1984 to 41.9% in 2006–2011. The addition of smoking to socioeconomic factors modestly increased the percentage mediated in 1981–1984 from 0.8% to 2.0% in 2006–2011 for males, whereas among females, the addition of smoking made a more substantial contribution to mediation of 3.0% points in 1981–1984 to 7.7% in 2006–2011. If nobody had smoked tobacco (but otherwise had identical socioeconomic position), ethnic mortality inequalities would have been 12.2% less for males and 21.2% for females in 2006–2011.
