The wealth (and health) of nations: a cross-country analysis of the relation between wealth and inequality in disease burden estimation

BACKGROUND: Gross domestic product (GDP) per capita is arguably the single most predictive determinant of health at the national level, yet such a measure fails to capture the complexity of wealth (and thus health) distribution within a population. Risk factors, health-seeking behaviour, and outcomes at the individual level have been shown to be associated with asset-based measures of wealth, which is more stable and consistently assessed than measured income or expenditure. Despite the potential utility of such estimates, currently existing wealth and inequality measures are not comparable across surveys, across countries, or across time. In this study, we quantify wealth inequality using an asset-based measure by country and year, from 1990 to 2010, and study associations with inequalities between countries in various measures of health. METHODS: We generate a global asset-based wealth index that is comparable across countries and over time using nearly 500 surveys from more than 140 countries, anchoring this scale on assets with low differential item functioning. We then translate this to an international dollar scale for the calculation of a modified Gini coefficient and other traditional measures of inequality, and investigate the relation between such measures and overall and cause-specific mortalities and selected disease incidence. FINDINGS: Including the more robust household asset data in estimates of economic status changes the global picture of income inequality. In some countries, our results diverge significantly from the World Bank's estimates. Globally, income inequality has been increasing over the past 20 years and is inversely associated with progress in life expectancy and mortality. INTERPRETATION: The observed associations between income inequality and health inequities add new evidence to the debate around the possible detrimental effects of greater income inequality. Understanding the contribution of income inequality to health over time and across countries is critical for designing policies to improve health outcomes. FUNDING: Bill & Melinda Gates Foundation.