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Income inequality and mortality
The world's wealth is becoming more concentrated. According to the 1996 United Nations Human Development Report , the world's 358 richest individuals control economic assets equivalent to the combined annual incomes of the poor countries that are home to 45% of the world's population. 1 In the past 20 years, many countries including the United States and Britain have experienced soaring rates of income inequality. Do these trends matter for the health of populations?
No one would dispute that poverty is bad for health. In general, the lower the material standard of living (as measured by indicators like income) the worse is the level of health, whether measured by mortality, morbidity, or quality of life. In the United States, which is supposedly the richest country in the world, poverty still accounts for nearly 6% of all adult mortality. 2
Aside from the evidence on absolute deprivation, there is growing evidence that the relative distribution of income in a society matters in its own right for population health. This thesis, which has become most closely identified with the work of Richard Wilkinson, 3 4 has been replicated in nearly a dozen studies internationally. 4 Although some questions have been raised about the international evidence linking income inequality to mortality, 5 three recent studies reported in this journalâ[euro]"two from the United States 6 7 and one from Britain 8 â[euro]"have suggested that income inequality predicts excess mortality within individual countries. In the American study by Kennedy et al , income inequality at the state level was strongly correlated with total mortality rates (r =0.54, P<0.05), even after median income, poverty rates, smoking prevalence, and race were taken into account. 6 Income inequality was measured in that study by the Robin Hood index, which is the proportion of aggregate income that needs to be redistributed from the rich to the poor so as to achieve equality of incomes. A 1% rise in the Robin Hood Index was associated with an excess mortality of 21.7 deaths per 100 000 (95% confidence interval 6.6 to 36.7), suggesting that even a modest reduction in inequality could have an important impact on population health. The maldistribution of income was related not only to total mortality but...