Michael Geruso and Dean Spears. The Likelihood of Persistently Low Global Fertility. Journal of Economic Perspectives 40 (1), Winter 2026.Haul 002, item 3
The Likelihood of Persistently Low Global Fertility
Michael Geruso and Dean Spears
p. 5
Fertility rates have fallen below two in many countries. A second trace in Figure 2 shows that in 1950, almost nobody lived in a country with a fertility rate below two. In 1975, about 15 percent of people did. By 2000, 40 percent of people did. And in the most recent estimates (for 2023), 67 percent of people in the world lived in a country with a fertility rate below two. Each of the three most populous countries—India, China, and the United States—is now below this threshold. The threshold of two is important because it means that fertility is below the “replacement level.” Below-replacement fertility at a national level does not necessarily imply a shrinking national population: National populations can grow, despite below-replacement fertility, due to migration. Even absent positive net migration, population sizes can continue increasing for a short period after birth rates fall below the two-for-two replacement rate because of improvements in mortality or because of the echoes of large cohorts from past decades. But over the long-term, populations with below-replacement fertility would shrink absent net in-migration.
As the editor marked it, matched word for word against the source.
1. Why it's here
An interesting paper by Michael Geruso and Dean Spears on falling fertility rates around the world. According to their data, 67% of the world’s population now lives in a country where fertility is below replacement.
First, a quick primer on what that means. Replacement fertility is the average number of children each woman needs to have for each generation to replace the one before it. It’s usually pegged at 2.1, though the exact number varies with mortality. If fertility holds at replacement, each generation is roughly the same size as the last. Below it, each generation is smaller than the one before. Today, most of the world outside sub-Saharan Africa has fallen below that line. In places like Japan and South Korea, the fall is dramatic. South Korea is at about 0.7, which has led to all sorts of apocalyptic proclamations about the future of the world.
In this paper, the authors dig into a weird statistical quirk of the most common measure, the total fertility rate, or TFR: what demographers call the tempo effect. The TFR is a snapshot. It takes the birth rate for women in each age group in a single year and adds them up. What it doesn’t measure is how many children women actually have over their lifetimes. So if women start having their first baby at 30 instead of 25, the TFR dips during the years that shift happens, even if each woman ends up with exactly the same number of kids.
To get around this, the authors use a different measure: completed cohort fertility, or CCF. It counts the average number of children actually born to women born in a given year, over their whole lives. Timing doesn’t fool it.
They also ask why fertility is falling, and tackle one popular explanation head-on: the supposed rise of the child-free. Using a decomposition analysis, they split the decline into two parts: more people having no kids at all, and parents having fewer kids. In 19 rich countries, comparing women born around 1956 with women born around 1976, more childlessness accounts for only 37% of the decline. The other 63% comes from parents choosing smaller families. In India, the picture is even starker. Comparing high- and low-fertility districts, childlessness explains just 6% of the gap; smaller families explain 94%. And yes, India as a whole is now below replacement, though, like any country, with vast regional variation.
Then there’s the question everyone wants answered: do birth rates bounce back on their own? The authors went through the Human Fertility Database and found 24 countries where cohort fertility fell below 1.9. Not one has seen a later generation climb back to replacement. There have been spikes, the Baby Boom being the famous one, but they were blips around a long-term decline. In countries with records going back to the 1800s, like France and Sweden, fertility has been falling for two centuries.
What about pronatalist policies? By 2015, 55 governments had explicit goals to raise birth rates, with baby bonuses, subsidized childcare, paid parental leave and the like. None has brought fertility back to replacement. Where studies find an effect, it tends to be small. Part of the problem is how these policies get evaluated. Most studies use methods like difference-in-differences that capture short-term changes in births in a given year. But a lot of the time, the policy just gets people to have kids earlier. If a woman who would have had a baby at 30 has it at 28 instead, births that year go up, but the total number of children she has stays the same. The policy is borrowing births from the future. Romania is the brutal example: when it banned abortion in 1966, the birth rate nearly doubled the next year, but lifetime fertility barely budged.
The authors’ bottom line is that a few thousand dollars in incentives can’t compete with life-defining decisions about what kind of family to build. Turning this around would take a profound structural, economic and cultural change in how societies treat parenting, a radical reorganization on a scale nobody has tried. Without it, sustained global depopulation is the most likely future. As they put it:
Our times … would be a historical anomaly that will come to an end.
Chilling, but there it is.
All in all, an interesting paper, worth your time. If you hate reading economics papers, this one is light on math. It’s free to download from the American Economic Association, and you can feed it to an LLM and argue with it, as I did. After reading it, of course. B.