When to have another baby: A dynamic model of reproductive decision-making and evidence from Gabbra pastoralists

Maximizing reproductive success involves having as many children as possible that can themselves reproduce successfully. Thus, when Gabbra parents decide to have another baby, they must trade off the probability that they will be able to afford to raise the child and marry it off successfully when it reaches maturity against the risk that feeding and raising that child would diminish the family herd, harming the marriage prospects of other children and possibly even leading to household destitution. Here I use a dynamic, state-dependent optimality model to analyze this trade-off. The decision to have another baby depends on household wealth and the number of children they already have. Parents should not necessarily reproduce at the maximum rate to maximize reproductive success, and the costs of marrying off a child have a large impact on the optimal family size. In the Gabbra, the cost of marrying off boys greatly exceeds the cost of marrying off girls. An analysis of demographic data from Gabbra households with a living husband and a first wife that had reached menopause show that probability of remarriage is strongly dependent on the number of children the first wife had. Number of sons has a much greater influence than number of daughters on the probability of a second marriage, as predicted by the model. Men are attempting to create the optimal family.