Selection and the Marriage Premium for Infant Health

Previous research has found a positive relationship between marriage and infant health. However, it is unclear whether this relationship is causal or a reflection of positive selection into marriage. In this paper, we use multiple empirical approaches to address this issue. First, we use the rich set of information available in the Natality Detail Files to control for selection into marriage along observable characteristics. We use a technique developed by Gelbach (2009) to determine the relative importance of different covariates, and show how selection into marriage has changed over time. Second, we construct a matched sample of children born to the same mother and exploit individual-level variation in marital status at birth. We apply fixed-effects and first-differences techniques to this matched sample to account for time-invariant unobserved characteristics. We find evidence of a sizable marriage premium. However, the premium fell by over 40% between 1989 and 2004, largely as a result of declining selection into marriage by race. Accounting for selection reduces OLS estimates of the marriage premiums for birth weight, prematurity, and infant mortality by at least half.