Most Children Now Grow Up With Fewer Siblings Than Their Parents Did
105 of 194 countries are below replacement fertility, and the world average is 2.17 against a replacement line of 2.1 — so childhood now has fewer people in it.
105 of the 194 countries profiled here have fertility below the replacement rate of 2.1, and the population-weighted world average is 2.17, which means the typical child today grows up in a smaller household than their parents did.
The world's population-weighted fertility rate is about 2.17. The replacement rate — the level at which a population holds steady — is about 2.1.
The gap between those two numbers is four hundredths, and it is the whole story of what childhood now looks like from the inside.
Where the world actually sits
| Countries below replacement | 105 of 194 |
|---|---|
| Population-weighted world rate | 2.17 |
| Highest | DR Congo 6.0, Chad 5.8, Somalia 5.8 |
| Lowest | South Korea 0.72, Puerto Rico 0.9, China 1.0 |
More than half the countries in this dataset are already below the line at which their population sustains itself. The world total is above it only because the countries above the line have large populations and young age structures.
What this changes inside a household
The demographic consequences get most of the coverage — ageing populations, falling school rolls, pension arithmetic. The household consequences get almost none, and they are what a parent actually experiences.
Fewer siblings means fewer built-in peers. A child with two siblings has a permanent social group at home. A child with none or one has to get it somewhere else — from school, from organised activity, from a screen. That is not worse, and there is no evidence that only children fare badly. It is different in a way that shapes how a week is organised.
More adults per child. Falling family size usually arrives alongside older parents and longer-lived grandparents, so the ratio of attentive adults to children rises. That is the mechanism behind a great deal of what gets described as generational personality change, and it is arithmetic rather than culture.
The second child is not half of two. Housing, equipment and most fixed costs are already paid. Per-child cost averages therefore mislead in both directions — they overstate the cost of a larger family and understate the cost of starting one.
The countries at the two ends
South Korea at 0.72 is the lowest rate ever recorded for a country. At that level each generation is roughly a third the size of the one before it — a child born there today will have, on average, fewer than one sibling, fewer than one cousin on each side, and a shrinking cohort at every stage of school.
DR Congo at 6.0 is at the other end, and it is also the country with the fastest-growing child population at +41% to 2040. A childhood there is still, typically, a childhood among many children.
Both are real. Neither is the world average, and the world average describes almost nobody.
What not to conclude from it
Not a judgement about family size. Nothing in this data says a particular number of children is better, and this site does not publish that view.
Not a prediction for any household. A national fertility rate is an average across millions of people, most of whom are not average.
Not settled as to cause. Why the birth rate is falling sets out what the evidence supports and what it does not — and the honest answer is that the decline is consistent across very different countries in ways no single explanation covers.
See the full ranking at total fertility rate by country, or what happens further down the sequence at what happens when a country runs out of children.