SEMINAR: Economics Research Seminar

We propose that the recent rise in the fertility rate observed in developed countries is the beginning of a broad-based increase in fertility towards above-replacement levels. Environmental shocks that reduced fertility over the past 150 years changed the composition of fertility-related traits under selection and temporarily raised fertility heritability. As those with higher fertility are selected for, the “high-fertility” genotypes are expected to come to dominate the population, causing the fertility rate to return to its pre-shock level. We show that even with relatively low levels of genetically based variation in fertility, there is a rapid return to a high-fertility state, with recovery to above-replacement levels usually occurring within a few generations. In the longer term, this implies that the proportion of elderly in the population will be lower and the proportion of working age higher than projected, reducing the fiscal burden of ageing on developed world governments. However, the rise in the fertility rate increases the proportion of dependent young, presenting other fiscal and policy challenges.