match adult children to their parents and siblings. In addition, we use exogenous variation in family size induced by the … children's educational attainment. However, when we include indicators for birth order, the effect of family size becomes … order has a significant and large effect on children's education; children born later in the family obtain less education …

While recent research finds strong evidence that birth order affects children's outcomes such as education and earnings … earlier born children have higher IQs. Our preferred estimates suggest differences between first-borns and second-borns of … birth order effects occur because later-born children are more affected by family breakdown. …