How material wealth influences age at first birth among Pimbwe women from Tanzania

Whether a woman has an earlier or later age at first birth may be influenced by the amount of wealth, or its variability. Theory predicts that women tend to delay their first birth when they have high levels of material wealth, and have it earlier when they experience high wealth variability. However, both theoretical and empirical work have focused mainly on the influence of these two aspects of wealth on age at first birth separately. Here, we study how current household wealth and short- and long-term wealth variability, together, influence the reproductive onset of women. We analyse longitudinal data from Tanzanian Pimbwe women (n=495) using Bayesian logistic regression models. Our results show that women who experience higher short-term variability have their first birth earlier, while those with higher current wealth and long-term wealth variability delay it. Although there are no clear differences between the wealth predictors, wealth variability emerges as relatively more important to predict age at first birth than current wealth. Our work contributes to ongoing efforts to disentangle how both the amount and variability of wealth influence the reproductive onset of women, shedding light on the mixed evidence linking wealth and reproductive strategies among women.