Income Inequality and Health: a review and explanation of the evidence

Abstract

Whether the scale of a society’s income inequality is a determinant of population health is still regarded as a controversial issue. We decided to review the evidence and see if we could find a consistent interpretation of both the positive and negative findings. We identified 169 analyses in 155 papers reporting research findings on the association between income distribution and population health. We classified them according to how far their findings supported the hypothesis that greater income differences are associated with lower standards of population health. Analyses in which all adjusted associations between greater income equality and higher standards of population health were statistically significant and positive were classified as “wholly supportive”; if none were significant and positive they were classified as “unsupportive”; and if some but not all were significant and supportive they were classified as “partially supportive”. Of those classified as either wholly supportive or unsupportive, a large majority (70 percent) suggest that health is less good in societies where income differences are bigger. There were substantial differences in the proportion of supportive findings according to whether inequality was measured in large or small areas. We suggest that the studies of income inequality are more supportive in large areas because in that context income inequality serves as a measure of the scale of social stratification, or how hierarchical a