This More or Less podcast episode investigates the United Nations' projections of fertility rates, specifically focusing on the unusual flatlining observed in Argentina's projected fertility rate after a period of decline. The interview with Patrick Gerland from the UN Population Division reveals that the UN's model relies primarily on historical fertility trends and a relatively simple autoregressive model, assuming stagnation once fertility rates fall below replacement level. This approach, while acknowledging its limitations in predicting ultra-low fertility scenarios, is deemed more neutral than attempting to incorporate complex economic and societal factors. The discussion highlights the uncertainty surrounding future fertility trends and the possibility that the UN's predictions might be underestimating the decline in some regions, using examples like Cuba and Singapore to illustrate varying trajectories.