Inequality of opportunity in body mass: evidence from Australia

This paper extends current knowledge about inequality of opportunity in body mass in Australia. Drawing on 2013 and 2017 Household, Income, and Labour Dynamics in Australia survey data, our empirical strategy comprises of mean-based and unconditional quantile regression techniques. We find that inequality of opportunity accounts for a non-trivial share of body mass inequality. Our results based on waist-to-height ratio reveal estimates of 10%–14%, which are much larger than previously published estimates based on body mass index (BMI). Our estimates are lower-bound values based on 13 observable circumstance variables. Relaxing the homogeneity assumption, for instance, increases estimates by 1.7–3 percentage points. Applying the Shapley–Shorrocks decomposition procedure, age and parents' socio-economic status are identified as leading circumstance factors. This finding is refined when quantiles of the body mass distribution are evaluated. Age's role is diminished at the clinically risky upper quantiles. By contrast, parents' socio-economic status is the single most important circumstance factor at the upper quantiles. Investigating by gender groups, inequality of opportunity is greater among women than men, with parents' socio-economic status playing a critical role in this disparity. Taking a life course perspective, circumstances' influence shows weakening over time, while effort is more impactful at later life stages. Overall, our findings underscore that anti-obesity campaigns should tackle early life social inequality, in addition to empowering personal responsibility later in life.