Why Is the Birth Rate Falling? What the Data Supports, and What Is Guesswork
Fertility is falling almost everywhere, and the confident single-cause explanations do not survive the country data. Here is what the numbers actually support.
Global fertility has fallen to roughly 2.2 births per woman, with South Korea lowest at 0.72 and DR Congo highest at 6 — a range so wide that no single cause explains it, though the decline tracks women's education and urbanisation more closely than it tracks income.
"The birth rate is falling" is one of those sentences that sounds like a single event happening to everyone at once. It is not. It is dozens of national stories moving at very different speeds, and the moment you look at them side by side, most of the confident explanations stop working.
Here is what the country-level data supports.
The range is the story
Across the 194 countries in our dataset, the total fertility rate runs from 0.72 to 6 — a gap of more than eight times between the two ends.
| Country | Births per woman | |
|---|---|---|
| Highest | DR Congo | 6 |
| Chad | 5.8 | |
| Somalia | 5.8 | |
| Lowest | South Korea | 0.72 |
| Puerto Rico | 0.9 | |
| China | 1.0 |
Replacement level — the rate at which a population holds steady without migration — is about 2.1. Most of the world's population now lives in countries below it.
What the data actually supports
Women's education tracks the decline more closely than income does. This is the most durable finding in the field, and it holds across countries that have almost nothing else in common. It is not that education makes people want fewer children in some direct way — it changes the age at which people start, and starting later mechanically compresses how many are possible.
Urbanisation tracks it too. In our data the most urban countries — Kuwait, Bahrain and Singapore at 100% — sit far below replacement, while the least urban skew high. Children are an economic asset on a farm and an economic cost in an apartment, and that arithmetic has not changed in a century.
Later starts compound. A country where the average first birth moves from 24 to 31 loses births even if nobody changes their mind about how many they want. Much of the measured "decline in fertility" is a decline in the time available for it.
What the data does not support
That it is mainly about money. This is where the evidence gets awkward for almost everyone's politics. Several countries have run substantial cash incentives — baby bonuses, extended paid leave, direct payments — for long enough to measure. The effects are small, and often turn out to be timing effects: people who were going to have a child have it slightly earlier, and the total does not move much.
South Korea is the clearest case. It has spent enormous sums over two decades and has the lowest rate in the world. Whatever is binding there, money is not loosening it.
That one country's explanation transfers. Korea's housing costs, its education spending arms race, its working hours and its division of domestic labour are frequently offered as the explanation. They may well be the explanation for Korea. They do not explain Puerto Rico at 0.9, and they do not explain why China and Singapore sit at 1.0 with very different housing markets and very different working cultures.
What this means for the next cohort
Generation Beta — everyone born from 2025 to 2039 — is the first cohort being born entirely inside this. The consequence is not a smaller world; it is a redistributed one.
In 64 of 194 countries, Generation Beta is projected to be larger than Generation Alpha. Nigeria goes from about 95 million Alphas to about 130 million projected Beta births. DR Congo rises 48%, Mozambique 43%.
In the other 130 it is smaller, sometimes dramatically. China roughly halves, from about 230 million to about 120 million. South Korea halves as well.
The centre of gravity of childhood moves substantially over a single cohort. That is the part worth arguing about, and it is almost entirely absent from coverage that reports a global average and stops.
The honest uncertainty
Global fertility has undershot the UN's medium-variant projections for most of the last decade. Projections built on those assumptions — including the widely quoted figure for how big Generation Beta will be — inherit that optimism.
Nobody forecasting fertility in 1965 predicted what happened next, and nobody forecasting it now has a better model than they did. The country rankings are measurements. The projections are assumptions with a number attached, and they should be read that way.
See the full ranking for all 194 countries on fertility rate by country, or the projected change in child population at under-15 population change to 2040.
The sourced rows are at birth rate statistics and fertility decline statistics.