Executive Summary: “An Assessment of Some Mechanisms Linking Economic Inequality and Infant Mortality” by Susan E. Mayer and Ankur Sarin

     Although research suggests that there is a strong link between inequality and infant mortality, when different offsetting factors are taken into account, the net effect is zero.  This paper takes a new approach in order to estimate the net effect of economic inequality on infant mortality.  It also examines the mechanisms through which inequality could affect infant death: nonlinear income effects, economic segregation, social resource allocation and relative deprivation.

     Few earlier studies consider the effect of inequality on neonatal mortality (i.e. death that occurs in the first 28 days after birth).  Also neglected are the aspects of society which inequality affects that could in turn impact infant mortality.  Although the positive and negative effects could yield a net result of close to zero, they are still worthy of analysis because social policies could then ameliorate the identified harmful effects of inequality.

      The authors thus put forth four mechanisms through which economic inequality could affect infant mortality.  First, there could be a nonlinear relationship between infant death and parental income: an extra dollar of income could improve the health of a low-income infant more than that of a high-income infant, and therefore, reducing income inequality while leaving the mean unchanged could reduce infant mortality.  Second, there could be segregation effects, as economic inequality increases economic segregation and higher levels of segregation are associated with higher levels of adult mortality.  Third, greater inequality could lessen infant mortality by increasing the level of redistribution of social resources, such as state spending on healthcare.  Lastly, “relative deprivation,” or upward social comparison, could negatively affect adult health through biological correlates of negative emotions and stress-induced risky behaviors, though this mechanism was not directly tested in the study.

     To assess these mechanisms and the net effect of inequality on infant mortality, the authors utilized data from the 1985, 1987 and 1991 United States Vital Statistics Linked Infant Birth and Death Records (LBID).  In addition, the authors used Census data to measure inequality at 1984, 1986, and 1990 (the years of conception) and levels of aggregation, and to control for states’ racial and ethnic composition, age composition, mean income, and census division, as well as mothers’ age and race.

     The study found that being born in a state with a high level of inequality increases the likelihood of infant death than birth in a state with less inequality.  This relationship remained statistically significant when state and maternal characteristics were controlled, though was weaker for post-neonatal mortality than for neonatal mortality.  On the other hand, state healthcare expenditures decreased a baby’s chance of neonatal death and death during the first year, and this reduction was due to additional spending per recipient.