The Depopulation Bomb

NATALIST PANIC IS rife nowadays. The White House is weighing initiatives to boost the number of births, ranging from a $5,000-per-baby bonus to awarding “National Medals of Motherhood” to mothers with six or more children. In March, the NatalCon gathering in Austin, Texas, declared that we're “living through the greatest population bust in human history.” In April, the tech billionaire (and father of 14 children) Elon Musk posted on X: “Low birth rates will end civilization.”

- RONALD BAILEY

And yet the world’s population continues to grow: 132 million people were born in 2024, boosting the global population by 71 million. Over the course of my lifetime, the U.S. population has risen from 160 million to 342 million and the world population has grown from 2.6 billion to 8.1 billion.

Still, given current trends, demographers calculate that world population will likely peak at just over 10 billion later in this century and then start to fall. Why? Because people are choosing to have fewer children. The total fertility rate—that is, the number of children the average woman has over the course of her lifetime—has been falling for decades. On a global scale, it has dropped from 5 kids in the 1960s to 2.2 children now. In the U.S., the rate has fallen from around 3.6 in 1960 to 1.6 today. That is well below the population replacement rate of 2.1 children per woman.

Even if Musk’s end-of-civilization worries are a bit hyperbolic, should we be concerned about impending depopulation? In After the Spike, the economic demographers Dean Spears and Michael Geruso argue, somewhat persuasively, that we should.

The book’s first section shows that current fertility trends will yield a spike in population followed by accelerating population decline. Since many people still believe that a world with fewer people is worth pursuing, the authors next turn to dismantling the case against more people.

The most infamous modern prophet of population doom is the Stanford biologist Paul Ehrlich. In his 1968 bestseller,