India, China, Europe, and the United States are on very different population paths

In 2021, around 1.25 million people died from diarrheal diseases. Around a third of these deaths were children.

Two main factors explain why so many children still die from diarrhea, especially in poor countries: the persistence of risk factors such as poor sanitation and unsafe water, and the lack of access to effective treatment.

Here, I want to focus on the second factor: access to a particularly effective treatment, known as oral rehydration therapy (ORT), which is essentially a mixture of clean water, salts, and sugar. Simple as it may sound, researchers writing in the medical journal The Lancet called ORT “potentially the most important medical advance of the 20th century.”

The chart shows how often this treatment is used in a selection of African countries. This is based on household surveys asking caregivers of children under five who recently had diarrhea whether they received ORT.

There are large gaps: in Chad and Cameroon, fewer than one in five children with diarrhea received the treatment. This reflects a mix of challenges, including low awareness of its benefits and expensive or inconsistent supply.

Importantly, though, the chart also shows that rates are much higher in Sierra Leone, where around 85% of children received ORT. This shows that much higher coverage is possible. Sierra Leone has implemented several successful policies, including free treatment for children.

Not every child with diarrhea needs this treatment — some recover without it, depending on their health and circumstances. But ORT is cheap, safe, and easy to give. In low-income settings, especially, offering it widely as a cheap preventive measure can make a big difference for those who need it.

Over the past four decades, the global number of people dying from cancer each year has doubled. This can look like the world is losing its battle with cancer: people are more likely to develop it, and we’re getting no better at treating it. This isn’t true.

There are, of course, almost 4 billion more people in the world than in 1980. And many of those people are older. This matters a lot because cancer rates rise steeply with age.

The chart shows three different measures. Total deaths just count how many people died from cancer; this is the number that has doubled. Crude death rates, shown in yellow, adjust for population size; the increase shrinks from more than 100% to around 20%. Age-adjusted rates, shown in blue, also account for the fact that countries have older populations today; we can see that the fully age-adjusted rate has actually fallen by more than 20%.

It means that for the average person, the likelihood of dying from cancer in any given year is now lower than it was for someone of a similar age in the past. The world still has a long way to go in preventing and treating cancer, but it’s wrong to think that no progress has been made.

The map shows which European countries saw an increase in population, and which saw a decrease in the year from July 2022 to 2023.

The regional divide is stark: most countries with negative population change are located in the eastern and southern parts of Europe, while countries in the west and north saw population growth.

We focus on 2022–2023 as they are the most recent years in the UN’s latest World Population Prospects, published in 2024. Temporary shocks can influence year-to-year population changes, but this regional pattern is not unique to this particular year: you see it in earlier years too, and it also shows up when you look at population change over longer periods.

A key driver of this is migration. Most countries in Western and Northern Europe have had positive net migration (i.e., more people arriving than leaving). Many countries in Eastern and Southern Europe, in contrast, have had more people leaving than arriving.

Fertility rates have been declining across Europe, and all of these countries now have rates below the replacement level. That means that across much of Europe, since deaths now exceed births, the population would be shrinking without migration. In Western and Northern Europe, positive net migration has been offsetting this.

It’s a widespread view that child deaths are still a pressing problem in poorer countries, but not in rich ones.

I don’t think this is true, and I want to illustrate it with one example from the United States.

In 2023, 30,200 children died in the US. In the same year, 22,800 Americans of any age were killed through homicide. You can see this in the chart.

Few Americans would argue that murders are a “solved problem”. And this is certainly not what you’d take away from the news. As we showed in a recent article, homicides receive disproportionate coverage in both left- and right-leaning media, relative to the number of people who die from them.

The everyday tragedies of children dying from preterm births, neonatal sepsis, and asphyxia do not get nearly the same attention, but are no less important. These are problems that we can still make more progress on.

We just lived through the period with the fastest population growth in human history. Six decades ago, there were three billion people on our planet. Since 2022, there have been more than eight billion people — an increase of five billion over this period.

It would have been impressive if food supplies had merely kept pace with population growth. But as the chart above shows, they grew even faster. On every continent, food supplies — measured by calories — grew faster than the population. This rise in food production per person was a major reason for the decline of extreme poverty and hunger.

To us, this chart documents one of humanity’s most extraordinary achievements.

A note on the data: Food supply estimates come from the Food and Agriculture Organization of the United Nations. We adjusted them to account for changes in region definitions and data coverage over time.

The economist Paul Krugman once said, “Productivity isn’t everything, but in the long run, it’s almost everything”. When workers can produce more value in the same amount of time, economies can grow faster, and living standards can rise.

The chart shows the productivity metric published by the Penn World Table for South Korea and Japan. It measures gross domestic product (GDP) per hour of work.

Since 2000, South Korea’s productivity has more than doubled, narrowing what was once a vast gap with Japan. It has now even surpassed its neighbor.

Many forces affect productivity, but one stands out in Korea’s case: its commitment to innovation. The country spends nearly 5% of GDP on research and development, among the highest shares in the world, and it files far more patents per million people than any other nation.

What does the British government spend its budget on? The chart shows spending broken down by category, scaled to £100. It combines both central and local government spending.

Social protection is the single largest item. Out of every £100 spent, £33 goes to it — more than health, at £19 per £100. The UK is typical in this regard — in every OECD country except the US, social protection is the biggest category.

Public services also account for a large share: £14 per £100. These include core government functions, foreign aid, and interest payments on government debt.

Education and economic affairs, which support the broader economy or specific industries such as fishing and manufacturing, are also prominent categories.