For example, in theory, increasing the affluence of the rich could have either detrimental or beneficial health consequences for the remainder of the population. Beneficial consequences could arise from positive externalities created by wealthy individuals, such as advanced medical technology, better schooling, or more crime prevention. In contrast, increasing the wealth of richer families could negatively affect health outcomes by increasing economic segregation and crowding out the concerns of the poor. Given that most of the recent increase in inequality in the United States has been associated with income growth among the middle and upper levels of the income distribution, rather than with income losses among the poor, documenting how and when income inequality affects mortality is important. Health Statistics Compressed Mortality File and the 1980 and 1990 decennial censuses.
All analyses are age-adjusted and control for the median level of household income in the state.
As a measure of overall income inequality, DDKL compute the ratio of the 90th to 10th percentiles of state household income. The remainder of the Letter summarizes their results. The average correlation for these two years is shown in the first bar of Figure 1 . A stricter test of the inequality-mortality association is represented by the second bar which reports the correlation between changes in inequality and mortality, by state, from 1980 to 1990. Disaggregating inequality To decompose the effect of overall inequality into inequality associated with deprivation at the bottom versus affluence at the top, DDKL use two detailed measures of dispersion.