Is Having Babies Contagious? Estimating Fertility Peer Effects Between Siblings

Models of fertility have long relied on peer effects to explain the large variance in birth rates across time and place within the developed world. However, little has been done using micro-level data to establish that fertility peer effects actually exist. I find that the probability of having a child rises substantially in the two years after one's sibling has a child. This contagion effect is strongest when substantial cost savings from coordination appear most likely and when the individual herself has little child-care experience and would thus rely heavily on siblings for information — further evidence consistent with peer effects.