Many countries have been facing intense heat this summer, and with predictions of a strong El Niño on the way, next summer could be even hotter. This has ignited debate on the need for cooling methods and technologies — most prominently, air conditioning (AC).

But how do rates of air conditioning usage vary across the world? Large international comparisons are hard to come by, but the International Energy Agency just published some new estimates for a select number of countries and regions.

The chart shows the estimated share of households with AC in 2025.

In Japan and the United States, AC adoption is almost universal; at least 90% of households have it. Most households in China also have AC; this share has increased rapidly over the past decade.

Adoption rates in Southeast Asia, Europe, and India are far lower, but for different reasons. In lower-middle-income countries like India, the reasons are often economic: AC would bring huge benefits, but many households cannot afford the upfront cost or the power to run it. Much of Southeast Asia faces a similar barrier.

In many European countries, it’s less of an economic barrier and more of a historical and cultural one. AC was not seen as a necessity because heatwave events were less frequent and intense than they are today. That is changing, and will continue to do so as the planet warms.

Most high-income countries have reduced road deaths substantially over the past decades. But the United States has made much less progress than other rich countries, and has even gone backward since the mid-2010s.

In this chart, I compare the trends for the US and a selection of other high-income countries to illustrate this point.

Consider Germany, which provides a useful comparison. In 1980, the US had about 25 road deaths per 100,000 people, and Germany had 22. But in the decades that followed, Germany’s rate fell steadily, while the US rate declined more slowly, and even rose again. In 2023, the last year in the data, the US rate was more than 4 times Germany’s.

In 2024, the National Academies of Sciences, Engineering, and Medicine in the US published a report that traces the gap to a mix of road-safety measures that other rich countries use more widely, such as speed and red-light cameras or lower limits where people walk.

There’s also a connection with how much Americans use their cars. In the US, people drive much more. However, that doesn’t fully explain the gap — US roads are also significantly more dangerous than those in Germany per kilometer traveled.

What we pay for something in a shop often doesn’t reflect its true cost. Producing goods causes damage through carbon emissions that drive climate change, but the receipts for that damage rarely show up in the price. The costs are often hidden and diffuse, but that doesn’t mean it isn’t real.

One way to make people pay the full cost is to introduce a carbon price. This can take the form of a carbon tax or a trading system, which caps emissions and lets companies buy and sell permits.

Many countries now do this. Around 30% of the world’s carbon dioxide (CO₂) emissions have a carbon price. In the chart, you can see that this has doubled in the last decade. The biggest part of this rise came from China’s introduction of a trading system in its electricity sector.

While more and more of the world’s production has a carbon price, most prices are incredibly low. In a recent article, we showed that most priced emissions were valued at $10 or lower. That’s well below most estimates of the “social cost of carbon”, which tend to be greater than $100 per tonne.

Simply having a carbon price is not enough. It also needs to be high enough to change what people buy and make low-carbon alternatives worth investing in.

Renewables supplied around 6% of Morocco’s electricity in 2000; by 2025, that share was four times as high.

That’s what the chart shows: the growing share of electricity production that comes from renewables.

Morocco’s rise stands out in the region for how it got there – several other African countries with rising renewables shares, like Sudan, have relied primarily on hydropower. Morocco, by contrast, has achieved it with wind and solar production, as part of a targeted policy push.

This has made Morocco’s electricity mix cleaner: each unit of electricity now comes with a larger contribution from renewables. But total fossil-fuel generation has not fallen. New solar and wind production has gone toward meeting rising demand, rather than displacing coal.

Morocco still burns nearly three times as much coal for electricity as it did in 2000, although coal generation appears to have plateaued in recent years.

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.

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.

Five years ago, almost no one in Latin America bought an electric car. Today, the situation is different: electric cars now make up a meaningful and fast-growing share of new car sales.

The chart shows this trend across several of the region’s largest car markets, alongside the US for comparison.

The data tracks the share of new passenger cars sold that are electric, which includes both fully battery-electric cars and plug-in hybrids.

In five years, Colombia went from nearly zero to 10%, catching up to the US.

In other countries in the region, adoption took off a bit later, but is now rising fast too. Mexico, for example, went from 2% to 7% in a single year (2024–2025).

An important part of this reflects policies. Many Latin American countries, like Colombia, offer tax breaks and other incentives for buying electric cars.

Dozens of companies worldwide develop large AI models, but it can be difficult to get a sense of where the most-used ones tend to come from.

OpenRouter is a large platform that allows users to interact with and write software on top of AI models through a single interface. It includes all the models from large companies like Google, OpenAI, Anthropic, Meta, DeepSeek, and Alibaba, as well as many, many others.

I analyzed the data published by OpenRouter on the 50 most used models each day since January 2025 and calculated the average monthly presence by origin country of the models.

As you can see on the chart, US-based companies still account for most models in OpenRouter’s top 50. But their presence has declined, and China-based companies have grown rapidly, from 5 models in the daily top 50 at the beginning of 2025 to 20 in May 2026.

Very few top-50 models come from companies outside the United States and China. Canada was represented early in 2025 by Cohere’s Command R models, while France remains represented by Mistral AI’s NeMo model.

A technology that more people use every year is, so far, almost entirely the product of two countries.

In the 20th century, obesity was a health problem that mostly affected today’s rich countries. In the 21st century, it has emerged as a health challenge almost everywhere. Many low- and middle-income countries have seen rapid increases in the share of people defined as overweight or obese.

In the chart, you can see this rise for Pakistan. In the last 20 years, the share of adults defined as overweight has more than doubled, and the share defined as obese has more than tripled. Now, almost 60% of adults are overweight, and one-quarter are obese.

These are modeled estimates from the World Health Organization based on national surveys of height and weight. Body Mass Index (BMI) is a person’s weight in kilograms divided by the square of their height in meters. An adult is defined as overweight if their BMI is 25 or greater, and obese at 30 or greater.

Pakistan’s own domestic surveys often report even higher figures; that’s because they have a lower BMI threshold for being overweight and obese, which reflects the fact that South Asian populations can have higher health risks at a lower level of BMI.

Obesity is a health problem because it increases the risk of developing a range of conditions, such as cardiovascular disease, strokes, diabetes, and various cancers.

In Europe, the supply of dairy products is far higher than in other parts of the world.

This chart shows milk supply per person across the world’s regions, with data from the Food and Agriculture Organization of the United Nations.

It’s based on supply — the amount of milk available for consumption — which includes consumer waste, so it is slightly higher than the amount that people actually consume.

As you can see, the per capita supply in Europe is more than two and a half times the global average. People across Africa and Asia have far less available.

These numbers include dairy products such as yogurt and cheese, based on how much milk is used to produce them, but they do not include butter.

How likely is it that a 15-year-old girl will eventually die from a pregnancy-related cause?

Researchers at the UN and the World Bank combined available birth and mortality data with statistical models to answer this question. Their estimates assume that the country’s fertility and mortality rates remain constant throughout the teenager’s lifetime (an important assumption I’ll get to later). The chart shows their results.

In Chad, the Central African Republic, and Nigeria, the estimated lifetime risk is around 4%. This is dire: it means about 1 in 25 girls would eventually die from a pregnancy-related cause.

Women in many other African countries also face substantial risks, and much of Sub-Saharan Africa has a rate above 1%. By comparison, estimates in most other regions are considerably lower, and across Europe the risk is below 0.1%.

The very high risks for the countries on the left of the chart reflect two factors that compound: they have some of the highest maternal mortality rates in the world, and the average number of births per woman in these countries is also high. They face a high mortality risk per pregnancy, multiplied by five or six pregnancies over a lifetime.

Maternal mortality rates per pregnancy and fertility rates are falling in these countries. Both of these declines would substantially reduce the lifetime risks. The results in the chart assume they stay at current levels, but that doesn’t have to be the case.

At the turn of the millennium, one-in-five adults in India smoked tobacco, and almost half of all adults were using any form of tobacco, including products that are chewed or sniffed.

But over the past two decades, rates of both have roughly halved. You can see this in the chart.

Some countries have seen a decline in smoking among men, but a rise among women. This is not the case in India: tobacco use has fallen substantially for both sexes.

This decline has huge implications. Each year, smoking causes almost one million Indians to die earlier than they otherwise would. Since smoking-related diseases can take decades to develop, this recent decline in smoking rates will result in fewer deaths in the future.

Smokeless tobacco tends to have lower health risks because people are not inhaling smoke. But it still increases the risk of oral, throat, and esophageal cancers, gum disease, and other conditions.

In the last two centuries, the price of lighting has decreased drastically.

You can see this in the chart, which plots historical data from Roger Fouquet. To allow for comparisons over time, the data is adjusted for inflation and expressed in prices for the year 2000.

In the early 14th century, one million lumen-hours — a standard lighting measure — would have cost around £34,000 in 2000 prices. By 2023, this had fallen to £2.15, a 16,000-fold decline.

Innovations in lighting appliances, fuels, infrastructures, and institutions during the 19th and 20th centuries made this progress possible.

To put this in perspective, consider that a standard 100-watt incandescent light bulb today can emit about 1,600 lumens. Therefore, running one such bulb for 24 hours would produce about 40,000 lumen-hours.

That means that 1 million lumen-hours today would require continuously keeping a standard 100-watt incandescent bulb on for about 26 days. Achieving the same amount of light with candles would require 120 candles burning at once for that entire period.

Most people today take the ability to switch on a light at night for granted. But those who live or have lived without artificial light can appreciate how important it is.