Non-Technical Summary:
In the U.S. today approximately 2 percent of children under age 18 are adopted. About half of these are adopted into families that also have biological children.
What does having an adopted sibling mean for biological children in the family? While the addition of another child to a family is expected to reduce parental time and resources for each child, is there anything special about having a sibling who was adopted that might influence a biological child’s development and outcome? This is a question that has been little studied yet its answer could be relevant to a large number of children and may yield new insights about within-family influences on child development.
In this paper we explore this question focusing on years of education as our measure of outcome because educational attainment is a key determinant of other developmental outcomes in adulthood, most importantly health and mental health in adulthood.
We draw upon two sources of data. One includes the children of a single birth cohort and is relatively homogeneous in that parents are high school graduates of a single state in a single year. This reduces unobserved factors such as different cultural acceptance of adoption and different state laws governing adoption.The second source of data is nationally representative and draws from several birth cohorts, thus extending generalizability of the findings.
We find large heterogeneity (based on sex, family income, and age difference) in the effects of having an adopted sibling. In general, the effects on sisters’ education levels are less pronounced than the effects on brothers’. For brothers, we find evidence that family income further moderates differential effects, where males from low-income families have lower education if they have an adopted sibling but males from higher income families do not. The effects are greater when the adopted sibling is close in age to the biological child.
Our results have implications for our understanding of family dynamics as well as how sex shapes educational attainments of children.