The Dangerous Allure of Low Fertility

Abstract: Stochastic population and wealth trajectories for societies as functions of fertility are modeled with a minimal, endogenous model of a simple foraging economy. The model is scaled to match human lifespans and overall death rates. Stochastic population instability at both the high and low ends of fertility are considered. Lower population levels, caused by low fertility, generate concerns on economic growth, military security, and international political power; while also seen by some as reducing ecological and environmental damage. The model shows that increasingly low fertility leads to both higher wealth and lower population levels. As society is encouraged by increasing per capita wealth to continue to decrease fertility, dangerous population regimes are reached where stochastic extinction becomes more and more likely.