U.S. State Variation in the Marriage Premium for Infant Health, 1990-2022

Emma Romell , University of Oxford; University of Wisconsin-Madison

In the United States, infants born to married parents are born at higher weights than infants born to unmarried parents. Comparative work finds cross-country variation in the marriage premium for birth weight, suggesting that social context conditions the extent of infant health inequality across families. I add to this literature by using data on more than 100 million births to examine intra-U.S. heterogeneity in the married-unmarried birth weight gap. I find tremendous variation in birth weight inequality, both across states and over time. In 2022, gaps in birth weight between infants born to married and unmarried parents was greatest in Mississippi at 218g and smallest in Hawaii at 85g. Most states have seen their marital status birth weight gaps decline since 1990; New Jersey experienced the greatest decline in its gap, from nearly 250g in 1990 to under 100g in 2022. Differences in the composition of married and unmarried parents within states account for between 0-40\% of gaps in birth weight between family types. Fixed effects models suggest that features of state context, such as the normativity of marital fertility and the degree of welfare generosity, may moderate the relationship between marital status and infant health. Findings provide new evidence on the scope of U.S. birth weight inequality.

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 Presented in Session P6. Health, Mortality, and Ageing 2