Does an Additional Nephew Increase Fertility? Identifying Fertility Contagion Using Random Fertility Shocks

Sara Cools, BI Norwegian Business School
Rannveig V. Kaldager, Statistics Norway and University of Oslo

Fertility contagion through social networks increasingly attracts the interest of demographers. Contagion is expected to be strong between individuals who relatively similar and keep in frequent contact, making it challenging to distinguish network effects from selection. We utilize random fertility shocks to identify fertility contagion -- taking contagion between siblings as an empirical example. We draw data from Norwegian administrative registers (N approx. 170 000 men and women), and use twin births and the sex composition of children as random fertility shocks. Preliminary results show that when a sibling has twins at second birth, ego's fertility is significantly and substantially reduced. Though fertility contagion is predominantly found to be positive, our results show that effects may also run in the opposite direction.