A large body of past research, looking across countries, states, and metropolitan areas, has found positive and statistically significant associations between income inequality and mortality. By contrast, in recent years more robust statistical methods using larger and richer data sources have generally pointed to little or no relationship between inequality and mortality. This paper aims both to document how methodological shortcomings tend to positively bias this statistical association and to advance this literature by estimating the inequality-mortality relationship. We use a comprehensive and rich new data set that combines U.S. county-level data for 1990 and 2000 on age-race-gender-specific mortality rates, a rich set of observable covariates, and previously unused Census data on local income inequality (Gini index and three income percentile ratios). Using panel data estimation techniques, we find evidence of a statistically significant negative relationship between mortality and inequality. This finding that increased inequality is associated with declines in mortality at the county level suggests a change in course for the literature. In particular, the emphasis to date on the potential psychosocial and resource allocation costs associated with higher inequality is likely missing important offsetting positives that may dominate.
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