The number that says the most about a country

It is not the size of the economy, the population, the literacy rate, or the number of doctors. The figure many of them reach for first is the infant mortality rate2: the number of babies, out of every 1,000 born alive, who die before their first birthday. The published figures run from around 2 per 1,000 in Japan, Finland and Iceland to around 70 in Nigeria and South Sudan, more than thirty times as high.

It sits between two related rates. The neonatal3 mortality rate counts deaths in the first 28 days, so it sits inside the infant rate. The under-five4 mortality rate counts deaths before the fifth birthday, so it contains both, and it is the child-mortality figure in the UN Sustainable Development Goals, which also set a separate target for deaths in the first month. All three are quoted per 1,000 live births5. They rank countries in much the same order, so this article moves between them.

Why this number and not another

A baby is the most sensitive instrument a population has. Adults die of things that accumulate over decades, such as heart disease, cancer and the slow wear of a hard life. Outside a pandemic or an overdose wave, those numbers respond to change slowly. Babies die of things that respond within a year or two: being born too early or too small, a birth with nobody trained to attend it, a chest infection, a bout of diarrhoea6 with no rehydration salts7 to hand, or malaria8 that a bed net9 would have prevented.

Most of those have a cheap, known fix. So the infant mortality rate tracks how rich a country is, but it tracks something else at least as closely: whether the basics reach the people who need them. It moves when clinics open, when clean water arrives, and when girls stay in school. A Lancet analysis of 175 countries attributed about half of the fall in child deaths between 1970 and 2009 to one thing: women gaining more years of education. A country can be poorer than its neighbours and do better on this measure, or richer and do worse, and either result tells you something the wealth did not.

The collapse

The long history of this number is the single largest good-news story in the whole of mortality statistics, and it is almost never told as one.

Around 1800, something like four children in ten worldwide died before their fifth birthday: roughly a third in the better-off parts of north-western Europe, closer to half across much of Asia and Africa. The world figure was still about a third in 1930. In England and Wales in 1900, roughly 150 of every 1,000 babies died before turning one. In 2023 the figure was 3.9. The world as a whole followed the same curve, later and faster.

Read the last two rows together. Between 1990 and 2024 the world's population grew by just over half. The number of babies born each year fell only slightly, from about 143 million in 1990 to about 132 million in 2023. Child deaths before the age of five fell anyway, from 13.0 million to 4.9 million. That is a drop of about 62 per cent: divide 4.9 by 13.0 and about three eighths of the old total remains. Almost nothing else in the mortality tables has moved like that in living memory.

Where children still die

Four point nine million a year is about 13,400 a day, and the deaths are not spread evenly. Sub-Saharan Africa and South Asia between them account for more than four in five of them. The highest national under-five rates, above 100 per 1,000 (one child in ten), are in just three countries: Nigeria, Niger and Somalia. Japan, Finland and Estonia are around 2 to 2.5. Set against those, a child in the first group is about forty to sixty times as likely to die before the age of five.

Just under half of all under-five deaths now happen in the first 28 days of life: 2.3 million of the 4.9 million. Most are from being born too early, from lack of oxygen during birth, or from infection. That share has been rising, not because newborns are dying more, but because deaths after the first month have fallen faster. Pneumonia10, diarrhoea and malaria still kill a great many children who survive that first month, but far fewer than they did, and the newborn deaths have proved the harder ones to prevent.

This shows up on the Ledger's country atlas. Neonatal disorders11 are the leading illness in twelve countries: Afghanistan, Côte d'Ivoire, Ethiopia, Liberia, Mali, Mauritania, Niger, Nigeria, Pakistan, South Sudan, Tanzania and Uganda. They sit among the five leading illnesses in fifty-six countries in all. Where the leading cause of death is illness in the first month of life, the mortality table has a shape no rich country has seen in living memory.

What it does to life expectancy

This is the arithmetic that makes the number so powerful, and it is the reason the life expectancy article on this site keeps returning to it. A period life expectancy12 is the average age at death of an imaginary cohort13. A child who dies in infancy enters that average as a lifespan of a few months. So every infant death pulls the average down by almost a whole lifetime.

Cut infant mortality from 100 to 50 per 1,000 and five children in every hundred survive who would otherwise have died in infancy. If those children live to about 65, they add a little over three years to life expectancy at birth: five lives of 65 years, shared across a hundred births, is 3.25 years. Adult death rates do not enter that sum at all. This is why the headline life expectancy figures for the poorest countries look so low. Their adults do die younger, but a large part of the gap is that so many of their children never become adults at all.

The catch: the worst numbers are the least certain

Here is the uncomfortable part. The countries with the highest child mortality are, almost by definition, the countries least able to count it. A death at home in a village with no registrar14 is not recorded anywhere. The rates for much of sub-Saharan Africa and South Asia are not counts but estimates, assembled by the UN's Inter-agency Group for Child Mortality Estimation from household surveys15, in which mothers are asked about every child they have borne and whether each is still alive.

Those surveys are carefully designed, and the estimates are the best available. They still carry uncertainty intervals16 that a single number quietly hides, and they lag: a survey reports on the years before it, not the year it is published. Somalia's under-five rate for 2024 is published as about 101 per 1,000. The 90% uncertainty interval around it runs from about 46 to about 223. When you see a child mortality rate for a high-mortality country, you are looking at a well-built model of the recent past, not a register of last year.

Why it is the number to watch

A country's infant mortality rate is a report on whether the basics arrive. It moves within years, not generations. It responds to things a government can actually do. And the history of child survival is proof that the mortality tables are not fixed. The share of children dying before the age of five was still about four in ten in 1900. It is now below one in twenty-five for the world as a whole (3.7% is about one in 27), and around one in four hundred where the basics are universal (about 2.5 deaths per 1,000). The Ledger counts deaths. This is the figure that shows the count can fall.

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Last reviewed: 5 October 2026