Income distribution and health: can polarization explain health outcomes better than inequality?

Utilizing data from the China Health and Nutrition Survey (CHNS) from 1991 to 2011, we aim to analyze the effects of income distribution on two risks for chronic diseases: body mass index (BMI) and blood pressure. Unlike the previous studies, we consider two different kinds of indicators of income distribution: inequality and polarization. Different from relative inequality indicators such as the Gini index, which measure income gaps only, the recently developed polarization indicator captures group clustering and social alienation, in addition to income gaps. Our empirical results demonstrate that both BMI and blood pressure are positively correlated with income polarization, while inequality is a weaker predictor of these health outcomes. Thus, polarization, rather than inequality, should be used when analyzing the relationship between health outcomes and income distribution. We also examine the polarization-to-health transmission mechanism using mediation and moderation analytic frameworks. The results suggest that social networks mediate the effect of polarization on BMI and neutralize the effect on blood pressure.