On this episode of Unsupervised Learning Razib has a wide-ranging conversation with Dan Hess, the man behind the More Births account on social media. An engineer with a large family in the DC area, Hess’ essays on topics like Israelis’ high birth rate have gained the attention of X, with an account that has come from a few hundred followers to more than 30,000 in 2 years.

Razib and Hess first review the birth-rate collapse seen worldwide in the past two decades. They discuss the relatively abrupt cultural pivot that has occurred since the turn of the century, with the end of the “overpopulation” narrative typified by Paul Erhlich’s Population Bomb, the rise of the “birth dearth” and the natalist movement. They talk about the most extreme cases of low total fertility rates (TFR) in Europe and East Asia, but also the decline in societies like the US, Latin America and the Middle East. Hess addresses both possible causes and possible solutions. They also discuss historical and demographic factors that impact fertility; for example, which religions have been the most pro-natalist? Hess also puts a particular focus on South Korea, the world’s most extreme case of a sharp decrease, with a TFR of about 0.70 children per woman (vs. 2.1 replacement), as well as exceptions to the rule like Haredi Jews and the Amish. Finally, Razib and Hess tackle why we should care about slower population growth in this century, from dependency ratios to the impact on cultural vitality.