Tobacco consumption in New Zealand: why did it fall?

To estimate the relative contributions of trends in smoking prevalence and trends in smoking intensity (average number of cigarettes smoked per day) to the observed decline in per capita tobacco consumption in New Zealand from 1984 to 2004.

Tobacco consumption and smoking prevalence time series data were sourced from Statistics New Zealand and the ACNielsen Omnibus Survey respectively and checked for accuracy against other sources. The contribution of changes in smoking prevalence to the observed decline in tobacco consumption was estimated by counterfactual modelling. The corresponding contribution of trends in smoking intensity was then calculated by difference.

Changes in smoking prevalence accounted for 48% of the decline in per capita tobacco consumption from 1984-89 and for 39% thereafter. Correspondingly, changes in smoking intensity accounted for 52% of the consumption decline during the first five years of the study period and 61% thereafter (i.e. from 1990 to 2004).

Understanding the relative contributions of trends in smoking prevalence and smoking intensity to the observed decline in per capita tobacco consumption is important, because the relationship between smoking intensity and health effects is non-linear. Our results indicate that the dramatic fall in tobacco consumption in New Zealand over the past 30 years will not be accompanied by an equivalent reduction in tobacco-attributable morbidity and mortality. Furthermore, our findings raise doubts as to how much longer tobacco consumption will continue to decline, given that smoking intensity is already low. The key message for the tobacco control program is to re-focus on helping smokers to quit and stay quit.