Many of us take artificial light for granted. Most of us use it daily: we can read, cook, and do tasks indoors; students can study at night; and our communities and homes are safer when not cloaked in darkness.

It’s not just light that has been transformative, but cheap light. The price of lighting has fallen by more than 99.9% since the 1700s.

Changes in what we use to power lighting have been crucial to the plummeting costs. This chart, based on data from Fouquet and Pearson, shows these changes from 1700 to 2000.

In 1700, the typical British household lit its evenings with candles. In the 18th century, they started using whale oil, and by the 19th century, they saw the rise of burning gas. Kerosene briefly provided a fifth of light around 1900. With each transition, lighting became more efficient, and the costs dropped. But the defining transition has been to electricity. It now provides almost all of the UK’s artificial light.

For hundreds of millions of the world’s poorest, lighting at night is still a luxury, and will remain so until they get access to electricity.

Explore what the cost and distribution of lighting tell us about human development →

For most of the 2010s, Ecuador had some of the lowest murder rates in Latin America. According to data from the UN Office on Drugs and Crime, rates were often three or four times lower than the regional average.

But as you can see in the chart, homicide rates have risen steeply in the last few years. From 2020 to 2023, rates increased more than fivefold. To put this in context: the number of people murdered each year increased from roughly 1,400 to 8,200.

Ecuador went from being one of the safest countries in the region to having one of the highest murder rates, not only in Latin America, but in the world as a whole.

This increase in violence has been linked to Ecuador’s growing role in international drug trafficking and competition between criminal groups. Large outbreaks of prison violence, often involving rival gangs, have also contributed.

Estimates of homicide rates can vary between sources; read our explainer on differences between them →

Go back to China in the 1960s, and you’ll find that the average person ate very little meat. This isn’t surprising: most of the country lived in extreme poverty and could not afford it. Meat consumption is strongly correlated with income: as countries get richer, they tend to have more diverse, meat-heavy diets.

However, as the chart shows, meat supply per person has increased significantly over the last sixty years. In 1962, annual consumption was just 4 kilograms per person. By 2022, it had increased almost 18-fold to 70 kilograms.

It’s not only the amount of meat consumed that’s changed: people in China also eat a more diverse mix. In the 1960s and 1980s, almost all meat came from pork. Today, pork still dominates, but it is joined by more poultry and beef.

This change in diet matters for various reasons. More diversified diets (which are not only about animal products) tend to be more nutritious than monotonous staple-heavy diets that are common for people living in poverty. But this increase in meat consumption also comes with a large environmental impact and consequences for animal welfare.

Explore how meat consumption has changed in your own country →

Scientists can make an enormous difference in the world.

Take the researcher Sarah Gilbert, who has dedicated her career to developing vaccines. Over the last two decades, she has contributed to vaccines against the flu, MERS, Nipah virus, and Rift Valley fever. When she heard about the outbreak in China in January 2020, she began working on a vaccine, just in case. By the end of that year, the vaccine against COVID-19 was approved, saving an estimated 6.3 million lives in the following year alone. Without this effort, we would have faced a much darker reality, marked by lockdowns, overwhelmed health systems, and widespread suffering.

This chart lists many such scientists whose work saved many people’s lives. The estimates are taken from the web publication Science Heroes, where you can find profiles of these scientists.

It’s difficult to estimate the exact difference particular innovations have made, and I take all such estimates with a grain of salt. None of these scientists did their work in isolation; their innovations were achieved thanks to collaborative efforts and the earlier work of other researchers.

Our team spends much of its time counting deaths, but it’s equally important to know the number of lives saved — even though it is harder to estimate and involves much larger uncertainty. It’s inspiring to be reminded that creative, enterprising, and tenacious people can enormously contribute to our lives.

Fritz Haber and Carl Bosch, who invented synthetic fertilizers, are at the top of this list. My colleague Hannah Ritchie wrote an article about the difference their work has made: How many people does synthetic fertilizer feed? →

According to official mining output records, Peru mined about 90 tonnes of gold in 2023, far ahead of any other South American country. That puts it within the world’s top 15 producers, just below the 10th place, as shown in the chart.

However, this official figure captures only part of Peru’s gold economy. Customs export data shows a striking discrepancy: about 80 tonnes of unaccounted gold in 2023, according to the Peruvian Institute of Economics. That’s gold whose value appears in export statistics but not mine-output records — and it is almost as large as the official figure based on mine records.

Some of this gap may be due to re-exports, inventories, or recycled gold. But given how big the discrepancy is, Peru’s authorities, researchers, and media see it as a practical indicator of the scale of informal and illegal mining. An article in The Economist, for example, compares Peru with other countries using this approach, and argues that gold has become more profitable than drugs for many gangs in South America.

Illegal gold mining is widely recognized as a major issue in Peru and the region, frequently linked to environmental damage and organized crime. This context matters today: the steep recent increase in gold prices raises incentives around unregulated extraction and trade.

→ Our Minerals Data Explorer has more data on metals, minerals, and mining. This United Nations report provides more information about illegal mining and its environmental effects.

This chart shows the share of people who say homosexuality cannot be justified across five of the world’s most populous countries.

Together, these countries are home to nearly half of the global population. And in all of them, most people still hold strong views against homosexuality. In Pakistan and Indonesia, it’s over 90%; in China, more than 80%. In India and Russia, these views are widespread, and they’ve increased in recent years.

That’s troubling. It’s hard to feel free, or even safe, when your sexuality is seen as something to condemn. In Western Europe and the US, negative views of homosexuality have dropped over the last 40 years.

Homosexuality is now legal in both China and India, but legal status doesn’t erase stigma. When large parts of society see same-sex attraction as morally wrong, laws alone are not a guarantee to protect people from harassment, exclusion, or violence.

Explore responses to this question in more than a hundred countries →