Kin Influences on Fertility: A Theoretical Framework Tested with a Review of the Literature

Rebecca Sear, London School of Hygiene and Tropical Medicine (LSHTM)
Cristina Moya, London School of Hygiene and Tropical Medicine (LSHTM)

Far from being an asocial process, reproductive decision-making is affected by family and other social networks. However, the direction and strength of kin effects is inconsistent across studies. Explaining this variation requires a better understanding of what various fertility outcomes mean functionally and of each individual’s strategic interests. A previous review demonstrated that kin have a beneficial impact on one aspect of female fitness: the survival of her children. However, fertility metrics are not as clearly related to a woman’s fitness. Furthermore, decisions regarding age at first birth, the pace of reproduction, and total number of births can be made independently of one another. Further complicating matters, woman and her kin do not always have the same strategic considerations. In this paper we develop a framework for comparing various accounts of why kin affect fertility. We test these possibilities using a database of kin effects on fertility from the literature.