Depression, anxiety, and other mental health problems are common everywhere. They are not confined to any particular income level.

But access to care is rare. In much of the world, people who struggle with their mental health have almost no psychologists or psychiatrists to turn to.

Mental health care is scarce in all places, but it is much scarcer in poor countries. Governments in high-income countries spend about $66 per person per year on mental health care, as the chart shows. In low-income countries, that figure is $0.04.

This gap in spending reflects a gap in people. As the WHO’s latest Mental Health Atlas highlights, there is roughly one psychiatrist per million people in low-income countries. High-income countries have 70 times more.

A recent study in the Lancet Psychiatry estimated that globally, only 9% of people with major depressive disorder receive a “minimally adequate treatment”. In high-income countries, it is 27%; in Sub-Saharan Africa, just 2%.

Hundreds of millions of people in poorer countries live with treatable conditions and have no access to a psychologist or psychiatrist. It is one of the largest gaps in global health — and one that receives remarkably little attention or funding.

There are efforts to close this gap without waiting for the workforce to catch up. One approach is to train lay counsellors — people without formal clinical qualifications who learn to provide psychological support. Randomized trials in India and Zimbabwe have shown this can be effective for depression.

Another approach is to use technology: apps and, increasingly, AI-based tools that can extend the reach of limited clinical expertise. These are not substitutes for a functioning mental health system, but in places where that system barely exists, they offer a starting point.

There are two ways to produce seafood: catch fish in the wild or farm your own. Seafood farming is often called “aquaculture”. Aquaculture is dominated by the farming of fish, but also includes other organisms, such as crustaceans and aquatic plants.

Aquaculture has grown rapidly over the last few decades. In fact, as the chart shows, it has overtaken wild catch since 2013.

This has relieved some pressure on wild fish stocks: if this increased demand for fish had been satisfied by wild catch, then many more would be severely overexploited.

Last year, three-quarters of the world’s countries had unemployment rates below 10%, according to data from the International Labour Organization. Colombia, where I come from, is in that group.

I initially found Colombia’s relatively low unemployment rate surprising, because it didn’t match what I could see around me: many people doing extremely precarious work.

This chart offers an explanation. It shows, for a selection of countries of different income levels, what share of workers hold informal jobs, meaning work that lacks social protection and basic employment rights (no guaranteed benefits, no formal safety net).

As the chart shows, in Colombia, that share is almost 57%. In many lower-income countries, the share is far higher.

The reality is that low unemployment and widespread informal work can, and often do, happen at the same time. The reason this isn't paradoxical comes down to how these statistics are defined.

To count as employed in labor statistics, a person only needs to have worked for at least one hour during the survey’s reference period, often the past week. The definition is broad and includes self-employment, selling things on the street, and unpaid work in a family farm or family business. Both formal and informal jobs are included.

This means the unemployment rate can remain relatively low in poor countries, not because most workers have found stable, protected jobs, but because many have been absorbed into informal employment.

The United Kingdom was the birthplace of coal. It has now, effectively, died there.

As shown in the chart, in the late 1980s, around two-thirds of the UK’s electricity came from coal. By the time I was born in the 1990s, this had dropped to just over half.

The use of coal has plummeted in my lifetime. It now makes up around 0.1% of the UK’s electricity.

Coal was first replaced by gas, but is now being pushed out by wind, solar, and biomass.

In a recent Data Insight, I wrote about how Argentina was one of the richest countries in the world at the beginning of the 20th century. Today, I want to follow up with a striking comparison between Spain and Argentina.

The chart shows GDP per capita for Argentina and Spain over the last two centuries. These are historical estimates from the Maddison Project, and the data is adjusted for inflation and differences in the cost of living.

When Argentina declared independence from Spain in 1816, the two countries had very similar GDP per capita. By the late 19th century, Argentina had become richer than its former colonial power, and it stayed ahead for many decades. Spain then started growing faster in the 1960s, and by the mid-1970s it had caught up.

Continued economic growth in Spain after the 1980s drove the large gap we see today. It kept GDP per capita on a steep upward path into the 21st century. Argentina, by contrast, grew more slowly and went through several economic crises, visible on the chart.

Today, Argentina’s GDP per capita is closer to my home country of Colombia than to Western European countries like Spain. This helps us see how much of a difference economic growth can make within just a few generations.

Forty years ago, young people had higher literacy rates in Sub-Saharan Africa than in South Asia. You can see on the chart that the region had a 10-percentage-point lead in 1985.

But things have changed a lot since then. Sub-Saharan Africa now lags by more than 14 percentage points.

While literacy has improved in both regions, it has done so much faster in South Asia. There, almost all young people have basic reading and writing skills. In Sub-Saharan Africa, most of them do, but there is still a significant lag behind other world regions.

In South Asia, the increase in literacy rates among young women has been particularly dramatic. In the mid-1980s, only around 40% had basic reading skills. That has more than doubled to over 90%, and the gap between young men and women has essentially closed.

When I first visited Buenos Aires some years ago, I was struck by how grand the city's historic architecture was. This is something that strikes many tourists: parts of the city feel closer to Paris than you’d expect from a country whose income level today is more similar to my home country of Colombia than to France.

This chart helps put that observation in perspective. It shows the ten richest countries in the world in 1910, according to GDP per capita estimates from economic historians.

By this measure, Argentina was among the world’s richest countries in 1910, ahead of several Western European countries, including Germany and France. It also stood clearly ahead of its peers in Latin America at the time.

But over the course of the 20th century, Western European economies grew far faster, especially after the Second World War, and Argentina fell behind.

A long-run perspective like this shows how much of a difference economic growth can make within just a few generations.

In 1965, the median age in the United Kingdom was almost twice that of China. Half of the people in the UK were younger than 34 years, and half were older. In China, this midpoint was just 18 years.

Within just a few generations, that age gap has closed.

As you can see in the chart, the median age in both countries is now 40 years. Both populations have aged, but the increase was far faster in China.

In the 1950s and early 1960s, China’s median age fell partly because of a fall in child mortality: birth rates remained high, and more children survived.

After that, the rapid increase is largely explained by a steep fall in fertility, and therefore in births. Before then, high birth rates meant that large cohorts of children were continually entering the population, keeping it young. When births fell, fewer children were added each year, and the large, earlier generations grew older.

China’s median age is expected to continue rising quickly: under the UN’s medium projections, it will be 10 years older than the UK's by 2050.

Throughout the entire 20th century, about 100 million people died earlier than they would have because of smoking. That’s a lot, but it pales in comparison to the expected numbers for this century.

Between 2000 and 2023 alone, smoking-related deaths are estimated at 163 million. You can see this comparison in the chart.

Some epidemiologists project that unless there is a substantial change in smoking uptake and rates across the world, there could be as many as one billion smoking-related deaths in the 21st century.

In the 20th century, most of these occurred in today’s high-income countries. In the 21st century, most will come from low- and middle-income countries.

Many of the people who are expected to die are smoking today, but even more are expected to be future smokers. Finding ways to help people stop smoking and prevent them from starting matters for keeping this huge figure in the millions, not billions.

At the turn of the millennium, 2.2 billion people in the world lived in extreme poverty. In international statistics, this means they survived on less than $3 per day (in today’s money).

In the two decades that followed, this number more than halved. You can see this decline in the chart.

This huge reduction was driven by rising incomes and poverty alleviation across East and South Asia. In Sub-Saharan Africa, the opposite happened: while the share living in extreme poverty declined, the total number increased.

Looking ahead, based on the latest available projections from researchers at the World Bank, this reduction in global extreme poverty is expected to end. In fact, numbers in 2040 might be higher than they are today.

This is because most of the extremely poor today live in countries with stagnant economies. If these do not see much stronger economic growth, the world will have nearly one billion living in dire poverty for decades to come.

Note that these projections are based on the latest growth projections from the World Bank and the IMF. From 2031 onward, poverty projections are based on the average growth rates observed from 2015 to 2024.