Is Having Babies Contagious?

Ilyana Kuziemko, assistant professor of economics at Princeton, has an interesting working paper entitled Is Having Babies Contagious? Estimating Fertility Peer Effects Between Siblings". The paper sets out to answer whether there are "sibling peer effects" in regards to fertility choices. Does one decide to increase the chances of having a baby when one's sibling has a baby? Turns out, the answer is yes. Kuziemko finds that the probability of having a child rises substantially in the first two years after one's sibling has a child. I found this quote particularly fascinating, though.

"The most striking finding is that fertility rises dramatically (30%) for both men and women after their sister has a child—yet the birth of a child to a brother appears to have no effect on an individual’s fertility. I interpret this result as supporting a cost-side mechanism. Mothers are more likely than fathers to decide whether to share child-care advice, whether to include nieces and nephews in their own children’s activities, and whether to provide hand-me-downs to nieces and nephews—and may be more likely to provide such services to their own siblings than to siblings-in-law."