Using quantile regression to examine the effects of inequality across the mortality distribution in the U.S. counties

► Quantile regression (QR) can add to analytical approaches used in the health and social science research. ► QR confirms that the inequality-mortality association is not constant across the mortality distribution of U.S. counties. ► Considering all covariates, inequality is not significantly related to mortality among lower 15 percentiles of U.S. counties. ► The traditional regression approach focusing on mean value can be only applied to the middle 20 percent of counties. ► Our findings suggest that the analytical issues should be reconsidered in the inequality-mortality research.