Many cities across East Asia and Latin America have grown quickly over the last few decades. Since 1950, São Paulo’s population has grown sixfold. Shanghai’s nearly tenfold.

This rapid growth is now ending. São Paulo is near its population peak, and Shanghai is projected to peak around 2050.

The fastest-growing megacities are now emerging elsewhere. In the chart, you can see various examples: Karachi in South Asia, and Dar es Salaam, Addis Ababa, and Luanda in Africa.

Luanda, the capital of Angola, is an interesting case. It gets much less attention than well-established megacities, but as the chart shows, it's on track to overtake São Paulo in about 20 years and Shanghai in about 60.

In this dataset from the European Commission's Joint Research Centre, only 24 of today’s 100 largest cities are projected to still be growing by 2100; of those, 12 are in Africa, and 5 are in South Asia.

Of course, these rely on projections — often many decades ahead — and those come with a lot of uncertainty. Nonetheless, they provide a useful perspective on what the future of cities across the world might look like.

Growing up in the United Kingdom in the 1990s and early 2000s, almost all the eggs in our supermarket came from battery hens, those raised in small wire enclosures.

The living conditions in these cages are terrible. Birds get the space equivalent of an A4 sheet of paper. They don’t have the room to carry out their natural behaviors, such as nesting, perching, or dust bathing.

That has changed in recent decades. You can see this in the chart, which shows the conditions under which eggs are produced in the UK. Free-range eggs have increased from just 10% to 75%.

The use of caged hens has fallen, and the types of caged enclosures have also changed. Battery cages were banned in 2012, so legally, all cages since then have been “enriched” ones, which provide slightly more space.

Still, these do not give hens the freedom and room they’d have in barns or free-range farms. Studies suggest that moving hens from enriched cages to cage-free systems reduces the time they spend in pain by more than half.

And given that most eggs in the UK are now free-range, it’s possible to reduce this pain even further.

The increase in the world’s population is not exponential. The global population is growing, but the growth rate has declined since its peak six decades ago.

The chart shows the annual rate of global population growth according to historical estimates and projections from the UN World Population Prospects.

The growth rate peaked in 1963 at over 2% per year, and since then, it has more than halved, falling to less than 1% by 2020.

The UN demographers expect rates to continue falling until the end of the century, eventually leading to negative growth rates and a shrinking global population.

A person’s access to doctors depends heavily on the income level of the country they live in.

High-income countries have around ten times as many doctors per person as low-income ones. You can see this in the chart, which shows the number of medical doctors per 1,000 people.

The global average is around 1.9 doctors per 1,000. Low-income countries have around one-fifth of that figure.

These figures include generalist physicians and specialists.

Chronic malnutrition in early childhood can slow development and growth, leaving children shorter than expected for their age. That’s the focus of the chart: the share of children under five who are stunted, meaning they are much shorter than expected for healthy growth.

The consequences of stunting persist beyond childhood, affecting both physical health and cognitive development.

Guatemala has one of the highest stunting rates in the world: almost half of children younger than five are stunted according to survey estimates published by the World Health Organization.

Guatemala’s rate is the highest in its region, by far. In the chart, you can see it compared to a selection of other nearby countries – its rate is twice that of Haiti, the next-highest country and a much poorer one.

My colleagues Hannah Ritchie and Tuna Acisu recently wrote about what countries with high stunting today can learn from Japan. Over the 20th century, Japan reduced childhood stunting from over 70% to under 5%, and the decline from around Guatemala's current level to under 5% took place within a generation.

In the thirty years since I was born, fertility rates in my country, the United Kingdom, have not changed much. In 1993, the fertility rate was 1.8 births per woman. Thirty years later, it had dropped only slightly, to 1.6 births.

Elsewhere, the change has been much more dramatic; fertility rates have dropped sharply and are now similar to those in the UK.

You can see this in the chart, which shows the change in fertility rates from 1993 (in blue) to 2023 (in red). In Qatar and Iran, rates dropped from almost 4 births per woman to 1.7.

Fertility rates have fallen a lot across Asia and South America, too — Malaysia and Colombia are two examples (my colleague Esteban previously wrote about the latter). This marks a much faster demographic transition than many countries experienced historically.

Convergence isn’t the whole story, though. Here, I’ve picked countries with fertility rates that are similar to the UK’s today. But some have fallen far below these levels: in Chile and Thailand, the fertility rate was 1.2 births per woman in 2023, and may have fallen even further.