February 10, 2025
The share of births that are twins has changed over time.
The chart shows data for France, Canada, the United States, and England & Wales in the Human Multiple Births Database.
As you can see, twin births have risen dramatically since the 1980s.
One reason is the use of reproductive technologies such as in vitro fertilization (IVF), which have made it possible for many more couples to conceive. During procedures like IVF, multiple eggs can be used at the same time to maximize the chances of a successful pregnancy, which can lead to twin births.
Another reason for the rise in twin births is that the average age of women at childbirth has risen. Older women are more likely to have twin births, even without using reproductive technologies.
Twin births are a chance event, but data shows they can also be influenced by societal changes and reproductive technologies.
Today
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.
June 20
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.
June 18
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.
June 16
Spending on the hardware that trains and runs artificial intelligence has grown rapidly over the past years. One of the clearest indicators of how rapidly spending has increased is the revenue of American chipmaker NVIDIA.
The company accounts for around 85% of the global market for AI chips. These are graphics processing units (GPUs), originally built for video games but well-suited to the parallel computation AI training requires.
The chart shows NVIDIA's quarterly revenue in US dollars, split by end market — sales to data-center customers (cloud providers and AI companies) in green, and sales for gaming, consumer devices, and cars in red.
In early 2014, data centers and AI accounted for just 5% of its revenue; gaming was the biggest single segment. Twelve years later, the ratio has flipped: data centers and AI now make up over 90% of revenue. The revenue in this segment has grown 1,300-fold over the period, from $57 million to more than $75 billion per quarter.
The data centers and AI segment was already growing fast between 2014 and 2022, with revenue doubling every 16 months on average. ChatGPT's release in late 2022, alongside the broader push to deploy AI at scale, has accelerated that pace: since then, revenue has doubled every 11 months.
June 13
How much of the world’s fish stocks are overfished? Fisheries scientists often answer this question with a specific metric: the “maximum sustainable yield” — this is the largest catch that can be taken from a fish stock without depleting it to the point that future catches decline.
When a stock is fished at a rate above this level, it is considered overfished.
The Food and Agriculture Organization (FAO) of the United Nations estimates that just over one-third of the world’s assessed fish stocks are overfished. As the chart shows, this has increased from around 10% in the mid-1970s.
Getting high-quality global estimates of this metric is difficult; many regions have formal assessments of fish stocks and catch rates, but many fish stocks across Africa, Asia, and South America are not assessed rigorously. To get global estimates, the UN FAO combines these formal assessments with expert opinion and extrapolations based on available national and regional data.
The FAO’s report — The State of World Fisheries and Aquaculture 2024 — provides more detailed breakdowns of which species are overfished.
June 11
On the Iberian Peninsula, Spain and Portugal have scaled up solar and wind power almost in step.
In the chart, you can see the share of electricity coming from solar and wind. Both countries generated over 40% of their electricity from these sources in 2025. That was higher than the European Union average of 30%.
The two countries have very similar geographies and share an electricity market. They also have weak connections to the rest of the European electricity grid, forcing them to generate clean power at home rather than rely on imports.
Wind power is more prevalent in Portugal, while solar is ahead in Spain.
June 9
For most of human history, more people were born each year than died. Populations grew very slowly for most of this history, then rapidly in recent centuries, as child mortality plummeted and people lived longer.
But this is changing. As the map shows, deaths now outnumber births in a growing number of countries across Europe and East Asia.
The balance of births and deaths tells us about a country’s “natural population change” — whether it would grow or shrink without any international migration. Where deaths outnumber births, the population will shrink unless enough people move in from abroad to make up the gap.
