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.

Just a decade ago, almost three times as much electricity in the European Union was coming from fossil fuels as from solar and wind.

But last year, for the first time, solar and wind produced more than coal, gas, and oil combined. They accounted for just over 30% of total electricity production.

You can see this rise of solar and wind — and fossil fuels’ decline — in the chart.

This record happened despite a poor year for wind output due to low wind speeds and a slight increase in gas to compensate for lower hydropower output from dry conditions.

Marriage is closely linked to decisions about having children in many societies. It also matters for legal rights, family finances, and many other aspects of life.

The age at which people marry has rapidly changed in many countries. The chart shows this by tracking the average age at first marriage among women, using records from national statistics.

In Portugal, Italy, and Spain, the average age at first marriage has risen rapidly and consistently. Portugal saw the largest increase: from around 26 years in 2002 to over 32 years by 2020. This is more than six years in less than a generation. It’s also the largest increase among the countries in the OECD Family Database with data available from the early 2000s up to 2020 (the most recent year with available data in the series).

Changes in the timing of marriage have come together with other related shifts. For instance, a growing share of people are not marrying at all.

4,510 objects were launched into space in 2025, surpassing the previous peak of 2,903 objects in 2023 by a large margin.

The data shows that US agencies and companies were responsible for launching 3,708 of these objects — 82% of the global total.

The vast majority of these American launches consist of small satellites deployed as part of large commercial “constellations”. These interconnected networks of satellites now account for the bulk of all objects sent into orbit.

The rapid growth of satellite constellations makes it possible to expand Internet connectivity, but it also increases concerns regarding space debris and the congestion of Earth’s orbital environment.

In the 1970s, oil spills from tankers — container ships transporting oil — were common. Between 70 and 100 spills occurred per year. That’s one or two spills every week.

This number has fallen by more than 90% since then. In the last decade, no year has had more than ten oil spills, as shown in the chart.

The quantity of oil spilled from tankers has also fallen dramatically. Over the last decade, the average is less than 10,000 tonnes per year, compared to over 300,000 tonnes in the 1970s.

In the past, forests around the world were cut down on a massive scale. We lost some of the world’s richest ecosystems.

In recent decades, the picture has become more complex. Deforestation has not ended, but it is no longer happening everywhere. Since 1990, some regions have continued to lose large areas of forest, while others have slowed this long-run trend — and even reversed it.

The map shows regional changes in forest area based on the latest data from the Food and Agriculture Organization of the United Nations.

Deforestation has been particularly large in South America and Africa. At the same time, the forested area has expanded in Europe, North and Central America, and large parts of Asia.

These gains show that deforestation is not inevitable. When pressure on land falls, forests can return.

The Netherlands was the first country to legalize same-sex marriage in 2001. Since then, almost 40 other countries have followed suit.

You can see this in the chart, based on data from Pew Research. By 2025, same-sex marriage was legal in 39 countries.

Last year, two countries were added to the total. Thailand became the first country in Southeast Asia to legalize same-sex marriage, and a same-sex marriage bill also took effect in Liechtenstein.