By now, you’ve probably heard that fertility rates are dropping all across the world. But when you dig deeper into the numbers, there’s a broader trend that doesn’t make much sense at first: for the first time ever, men are having fewer children than women.

According to a new modeling study, the global average number of children a man is expected to have over his lifetime fell below that of women in 2024. This measure is known as the total fertility rate, or TFR. It’s mostly, if not almost entirely, been used throughout its life to track women, whose fertility rates have declined from 4.9 children per woman in 1952 to roughly 2.3 in 2023. For men, researchers had to estimate indirectly using population data. Until recently, men have averaged slightly more children than women. Times have changed, and that gap has closed, and now it has fully reversed.

All of this comes to us via a study published in PNAS, which explains that the reason for all this isn’t a cultural shift but rather a demographic one. More men are surviving to and through reproductive age than in previous generations, when something—diets, excessive drinking, excessive smoking, etc.—would’ve usually taken them out. There used to be a natural birth ratio of about 105 boys for every 100 girls, but improvements in survival over the years meant that a surplus of men isn’t disappearing early in life.

Instead, that carries over into adulthood, increasing the number of men relative to women, and lowering the average number of children per man.

For the First Time Ever, Men Are Expected to Have Fewer Kids Than Women

What’s interesting is that the shift isn’t exactly new, particularly in North America and Europe, where it actually happened decades ago. What is new is that it’s finally reaching Asia. Sub-Saharan African nations probably won’t see the same pattern until later in the century.

The Asian version of it has a small twist. There is a sharp imbalance due to sex selective abortion, which pushes birth ratios in countries like China and Vietnam to around 110 boys per 100 girls. That means there are more men entering adulthood than there are women to have kids with.

In practical terms, this means we are increasingly living in a world where a growing share of men will remain childless, especially in parts of the world where those gaps are wider. Over time, that could translate into more elderly men without much, if any, support from their families, increasing pressure on social and elder care systems.