Association of State-Level Tax Policy and Infant Mortality in the United States, 1996-2019

Abstract

ImportanceInfant mortality in the United States is highest among peer nations; it is also inequitable, with the highest rates among Black infants. The association between tax policy and infant mortality is not well understood.ObjectiveTo examine the association between state-level tax policy and state-level infant mortality in the US.Design, Setting, and ParticipantsThis state-level, population-based cross-sectional study investigated the association between tax policy and infant mortality in the US from 1996 through 2019. All US infant births and deaths were included, with data obtained from the National Center for Health Statistics. Data were analyzed from November 28, 2021, to July 9, 2022.ExposuresState-level tax policy was operationalized as tax revenue per capita and tax progressivity. The Suits index was used to measure tax progressivity, with higher progressivity indicating increased tax rates for wealthier individuals.Main Outcomes and MeasuresThe association between tax policy and infant mortality rates was analyzed using a multivariable, negative binomial, generalized estimating equations model. Since 6 years of tax progressivity data were available (1995, 2002, 2009, 2012, 2014, and 2018), 300 state-years were included. Adjusted incidence rate ratios (aIRRs) were calculated controlling for year, state-level demographic variables, federal transfer revenue, and other revenue. Secondary analyses were conducted for racial and ethnic subgroups.ResultsThere were 148 336 infant deaths in the US from 1996 through 2019, including 27 861 Hispanic infants, 1882 non-Hispanic American Indian or Alaska Native infants, 5792 non-Hispanic Asian or Pacific Islander infants, 41 560 non-Hispanic Black infants, and 68 666 non-Hispanic White infants. The overall infant mortality rate was 6.29 deaths per 1000 live births. Each $1000 increase in tax revenue per capita was associated with a 2.6% decrease in the infant mortality rate (aIRR, 0.97; 95% CI, 0.95-0.99). An increase of 0.10 in the Suits index (ie, increased tax progressivity) was associated with a 4.6% decrease in the infant mortality rate (aIRR, 0.95; 95% CI, 0.91-0.99). Increased tax progressivity was associated with decreased non-Hispanic White infant mortality (aIRR, 0.95; 95% CI, 0.91-0.99), and increased tax revenue was associated with increased non-Hispanic Black infant mortality (aIRR, 1.04; 95% CI, 1.01-1.08).Conclusions and RelevanceIn this cross-sectional study, an increase in tax revenue and the Suits index of tax progressivity were both associated with decreased infant mortality. These associations varied by race and ethnicity. Tax policy is an important, modifiable social determinant of health that may influence state-level infant mortality.