We often hear that "people in Japan live to 84 on average". The sentence is true, but it's often misunderstood. It doesn't say that every Japanese person lives to 84. Some die at 60, some at 100. So what exactly does this number measure, and why is the gap between countries so big? In this article, we'll simplify the concept and look at the reasons behind the gap. The figures are approximate values taken from the UN World Population Prospects 2024 and World Bank data.
What does life expectancy at birth measure?
Life expectancy at birth is an estimate of how many years babies born in a given year would live on average, assuming that year's death rates stay the same throughout their lives. In other words, it isn't a prophecy; it's a summary drawn from one year's mortality table. In reality, medicine advances and death rates fall, so a baby born today will often live longer than that figure.
There's one more important detail: this is an average, not the most common age at death and not the median. An average is strongly affected by very early deaths.
How do infant deaths pull the average down?
Let's think through a simple example. These numbers are hypothetical and only meant to show the logic. In a group of a hundred people, say ten die at age one and ninety live to seventy. The average from (10 × 1 + 90 × 70) / 100 comes out at about 63 years. If no one in the same group had died as a baby, the average would be 70. The early deaths of ten people pull the average down by about seven years.
The real world works in a similar way. In Chad, the under-5 mortality rate is about 107 per thousand; in Japan, about 2 per thousand. Chad's average life expectancy is about 53, Japan's about 84. A large part of this gap comes from losses in infancy and early childhood. In Chad, a person who makes it past age five can expect to live considerably longer than the figure at birth. So saying "nobody in that country makes it past 50" would be wrong; the real problem is that so many children are lost in their first years.
Highest and lowest life expectancy
Among the 70 countries in the game's dataset, the highest and lowest values are as follows (approximate, in years):
| Highest | Years | Lowest | Years |
|---|---|---|---|
| Hong Kong | 85 | Chad | 53 |
| Japan | 84 | Nigeria | 54 |
| South Korea | 84 | Somalia | 56 |
| Switzerland | 84 | Côte d'Ivoire | 59 |
| France | 83 | Mozambique | 60 |
| Italy | 83 | Burkina Faso | 60 |
Turkey sits in the upper middle of this list at about 78 years; the UK is a little higher, at about 81. Between the extremes lies a distance of more than 30 years.
Why is the gap so big?
There's no single reason; several factors feed into one another.
Access to health care
Having a midwife or doctor present at birth, treating infections with antibiotics and monitoring chronic diseases all noticeably extend lifespan. Distance from a health facility makes that access harder in rural areas.
Vaccines
Vaccines against diseases like measles, tetanus and polio have sharply reduced child deaths. Smallpox was wiped off the planet in 1980 thanks to vaccination. How widely vaccination programmes reach people still differs between countries.
Clean water and nutrition
Dirty water is one of the main routes for diarrhoea and other infectious diseases. Malnutrition weakens the immune system and raises the risk that an illness turns deadly. Access to clean water and regular food varies enormously between countries.
Income
Higher income means better nutrition, hygiene, housing and health spending. In the dataset, income per person and life expectancy generally rise together: all eight countries in the dataset with income per person of about 2,000 dollars or less (Chad, Somalia, Mozambique, Niger, DR Congo, Madagascar, Yemen, Afghanistan) have a life expectancy of 65 years or less. But the relationship isn't linear; past a certain income level, the gains slow down. And some middle-income countries have reached a higher life expectancy than their income would predict, thanks to investment in their health systems.
Conflict and instability
Wars don't only cause deaths directly. They also disrupt hospitals, schools and food supply chains. In the countries marked as conflict zones in the dataset (such as Somalia, Mali, Yemen and Afghanistan), life expectancy is between about 56 and 67 years, far below that of several high-income countries.
The historical rise: a story of two hundred years
For most of human history, the average lifespan was much shorter than it is today. Estimates suggest that until fairly recently, life expectancy at birth hovered somewhere in the 30s and 40s. The main reason was that large numbers of children died from diseases that vaccines can prevent today. According to UN data, the world average rose from about 46 years in 1950 to about 73 years today. In a little over half a century, the average gained 27 years.
Most of this rise came from falling child mortality. Today, in high-income countries, progress in old age (heart disease and cancer treatment) raises the average more slowly; in low-income countries, getting through childhood still brings big gains. That's why closing today's large gap depends first and foremost on reducing deaths at young ages.
Life expectancy and lifespan aren't the same thing
These two ideas often get mixed up. Lifespan is the number of years a person actually lives. Life expectancy is an average calculated for a group, and it only becomes final after everyone in that group has died. Expectancy can also be recalculated at any age: the remaining life expectancy of someone who has reached 65 is different from life expectancy at birth, because that person has already left the risks of childhood behind. That's why plenty of people reach 80 even in countries with low life expectancy; their share is just smaller.
Another distinction is about healthy life expectancy. Living long doesn't mean those years are healthy. Some countries are very good at extending life, but part of the final years is spent in illness. The health indicator in the game reflects this nuance only very roughly.
How is life expectancy used in the game?
In Birth Lottery, each country's life expectancy is used to calibrate the curve that determines your character's lifespan. On top of that, the family's income bracket pulls the expectancy up or down a little. The chance of dying in infancy and early childhood is set directly by the country's under-5 mortality rate. On the results screen, you see your character's lifespan side by side with the country average. Sometimes you live far beyond the average, sometimes you fall far short. It's a small reminder that the average isn't every individual's fate.
If you're curious about the overall effect of birthplace on a life, have a look at the birth lottery article. To try out a life of your own, go back to the game.