A key factor in population projections is the fertility rate, particularly how it might change over time. When University of Pennsylvania economist Jesús Fernández-Villaverde calculates global fertility rates, he finds them “falling much faster than anyone had realized before.” Something more like that UN Low Scenario in the above chart. As Fernández-Villaverde (I will be referring to several of his papers and essay throughout) told me in an enlightening Faster, Please! podcast:
So I look at the fertility of the planet as a whole in 2023. According to my calculations, it’s already 2.2. That means that the planet in 2023 — I’m not talking about the United States, I’m not talking about North America, I’m not talking about the advanced economies, I’m talking about the planet — is already below replacement rate. Which means that the world population will start falling some moment around the late 2050s to early 2060s]. Of course, this depends on how people will react over the next few decades, how mortality will evolve. But what I want the listeners to understand is, for the very first time in the history of humanity — humans have been around for 200,000 years — we are below replacement rate in terms of fertility. … My argument is the United Nations is underestimating how fast fertility is falling. Instead of 2084, I’m pushing this to 2060, let’s say. And instead of 9.7, I will say that we will peak around 9.2, 9.1, and then we are going to start falling.