A Research Note on the Identification and Interpretation of Parenthood Age Effects

In this research note, I contend that identifying and interpreting parenthood age effects is challenging. The challenge lies in separating the effects due to children being born to a later calendar year (child’s birth year effects) from those due to being born to an older parent (parenthood age effects per se). I draw the analogy with the fundamental problem of age-period-cohort analysis and show how a bounding approach proposed by Fosse and Winship might be helpful to elicit and address this challenge. My analysis, focusing on children’s educational attainment using data from Belgium, Germany, the Netherlands, and Sweden, reveals that child’s birth year effects can indeed be non-trivial. However, they might vary substantially across countries and cannot account fully for delayed parenthood advantage as argued in some previous research. I also show that the magnitude of child’s birth year effects is critical for identifying the shape of parenthood age effects and thus qualitatively different conclusions about optimal childbearing age.