Using genetic markers as instrumental variables to unravel the link between education and fertility

Nicola Barban, University of Groningen
Melinda Mills, University of Groningen
Jornt Mandemakers, University of Groningen
Harold Snieder, University of Groningen

The relationship between education and fertility has been a central focus within demography and related social sciences. Higher education is often associated with higher age at first birth and lower number of children, especially among women. The goal of this paper is to dig deeper into the relationship between education and fertility and explore the causal relationship by using genetic markers as instrumental variables. Specifically, by using the genetic markers for educational attainment from a recent GWAS (genome-wide association study), we attempt to unravel the causal relationship between education, age at first birth (AFB) and number of children ever born (NEB). Our results using data from three large samples in contemporaneous western populations (LifeLines, TwinsUk and HRS) show that education is not causally linked to lower fertility or higher age at first birth. We suggest that the observed association between fertility and education is mainly affected by unobservable factors.