Improved crop yields have allowed the world to feed billions more people while sparing forests and other land from agriculture.

Global yields of cereal crops have tripled since 1961. As you can see in the chart, they have increased in all regions.

However, yields across most African countries have lagged behind. At 1.7 tonnes per hectare, they’re still less than half the global average of 4.2 tonnes.

This is bad for farmers: they get much smaller harvests and live on much lower incomes. It makes it harder for countries to feed their populations. And it’s a problem for biodiversity: lower yields mean that farmland has to expand into wild habitats.

Increasing agricultural productivity — particularly across Africa — is one of the biggest challenges of this century.

In recent decades, sub-Saharan Africa has been the world’s fastest-urbanizing region.

The region’s most populous country, Nigeria, shows the scale of that change. In 1950, only around 1 in 10 Nigerians lived in a city. Today, it is nearly 1 in 2.

As you can see in the chart, over the same period, the share living in rural areas fell, but so did the share living in towns and suburbs, which had been the largest group in 1950 by a substantial margin.

Nigeria’s population became much more concentrated in cities — both because people migrated into established cities, and because new ones emerged as towns and suburbs grew dense and large enough to be classified as cities.

In early-industrializing countries, rapid urbanization was often closely tied to industrialization. Today, in many lower-income countries, including across much of sub-Saharan Africa, it is happening under different conditions.

Since the agricultural revolution, the majority of the labor force in countries like France, the United Kingdom, Italy, and the Netherlands worked in farming.

But over the last few centuries, this share has plummeted. Today, less than 5% of the workforce is employed in agriculture, and in many cases, it’s just a few percent.

This trend is shown clearly in the chart, which is based on data from the International Labour Organization and historical reconstructions by Broadberry and Gardner (2013).

The chart also includes the even steeper decline in agricultural employment in China over the last 40 years, as people have shifted to manufacturing and services.

Many other middle-income countries are on a similar trajectory, moving through this transition faster than European countries did in the past.

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.