The pattern of association between U.S. economic indicators and infant mortality rates at the state level

This cross-sectional ecological study examines the pattern of association of state income and income inequality (measured by Gini coefficient) with state infant mortality rates (IMRs) in the U.S. Scatter plots and correlation coefficients were used to examine bivariate associations and bubble plots to examine three-way relationships. Infant mortality rate was positively associated with Gini (R=0.397, p=.004) and negatively with income (R=-0.482, p <.001). However using Black and White IMRs, the associations with Gini were non-significant, but with income remained significant. The bubble plot of Gini versus White IMR (income represented by bubble size) showed increasing IMR as Gini increases and income decreases, except for a subgroup of high-gini, high-income states with low IMRs. State income appears to be a stronger and more consistent predictor of U.S. IMRs for both Black and White races and can explain the pattern of association of White IMR with state Gini coefficient.