Inequality in health within the United Kingdom has been widely discussed in medical, health, and social science journals, with the most recent data showing a widening of inequality between areas of the UK.1 Such inequality is also the focus of several government targets. In other wealthy countries inequality in health is both widely studied and subject to government attention.2 Recent political events such as the Make Poverty History campaign, the Live8 concerts, the G8 summit in Scotland, the World Trade talks in Hong Kong, and the broader background of “globalisation” have turned attention towards the global picture. In this article we ask two questions: what is the state of inequality in health and wealth across the globe? and, is inequality increasing or decreasing over time?

Data from the United Nations Organisation can be used to answer the first question,3 4 but a suitable measure of inequality is needed to answer the second question. Moser et al suggest using a novel measure of dispersion to track trends in the distribution of global mortality over time—the dispersion measure of mortality.5 They claim that “the dispersion measure of mortality has advantages over other commonly used summary measures of mortality contrast that only use information from the extremes of the mortality or socioeconomic distribution and do not weight for size of the unit.”5 We use another well established measure of inequality, which has the same attributes but is simpler to interpret and compute and is more informative—the slope index of inequality.6 The index can provide a simple measure of the size …