> Based on his analysis, the single biggest effect on fertility is the education of women. Although it's not surprising that controlling for education of women

> Based on his analysis, the single biggest effect on fertility is the education of women. Although it's not surprising that controlling for education of women would provide a better model fit, it seems unlikely to me that this is the main causal relationship. I think logic and evidence suggest that the main driver of fertility is child mortality. Humans appear to adjust fertility to maximize the probability that their offspring will successfully reproduce. Higher child mortality in a population tends to result in higher fertility as insurance against loss of a child [1]. Lower child mortality tends to result in lower fertility. The human species would not be around today if we lacked a natural tendency to place utmost priority on offspring reproduction success. Parents must trade off the number of children they have versus the quality of care per child. Our current rate of child mortality reduction is shifting the optimal strategy to fewer children and higher quality of care per child. I see improved education of women (and men) as largely a consequence of this trend. I expect this will continue until disrupted by high-mortality events such as natural disasters, disease, or major wars. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411230/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411230/