March 18, 2025
Putting a number on “happiness” is hard. But one way to better understand how satisfied people are with their lives is to ask them.
Self-reported life satisfaction is one key metric that researchers rely on. Respondents are asked to rate their lives on a 10-step ladder, where 0 represents the worst possible life, and 10 is the best.
The chart shows self-reported life satisfaction measured against gross domestic product (GDP) per capita. The two are positively correlated: people in richer countries tend to be more satisfied with their lives.
Of course, income is not the only thing that matters. You can also see the large spread of values for countries with similar levels of GDP per capita. For example, South American countries tend to have higher happiness levels than those in other regions.
Yesterday
The world's population has more than doubled over the last 60 years, but global food production has managed to keep up.
The chart shows the change in four indicators since 1961: cereal production, cereal yields, land use for cereals, and population. Each metric is expressed in its relative change since 1961 (which is given a value of zero).
Cereal production has increased by 3.5-fold, more than the 2.6-fold growth in population. That means production has grown faster than the population, and the world produces more cereal per person than 60 years ago.
We can also see what has driven this increase. You can grow more food by either increasing crop yields or using more land. While land use has increased, most of this growth has come from higher crop yields. This has spared some natural habitats from being converted into farmland.
Read more in my article on the Green Revolution and food production →
March 17
When we emit carbon dioxide (CO2) into the atmosphere, most of it stays there for centuries or millennia. This means that CO2 emitted even a century ago has contributed to the rising temperatures we see today.
In other words, how much the climate warms depends on how much cumulative CO2 is emitted over time.
The chart shows the ten countries with the largest share of the world’s historical emissions, based on cumulative emissions from fossil fuels and industry since 1750.
The United States has contributed the most, accounting for almost one quarter. This is followed by China and Russia.
There are many other ways to understand contributions to climate change – explore data on annual, per capita, and trade-adjusted emissions →
March 14
Global average yields of cereal crops have tripled over the past 60 years. This has been crucial to feeding a growing population while sparing natural habitat from expanding agricultural land.
However, some cereal crops have seen much larger gains in efficiency. Maize (corn) and rice achieve the highest yields and have seen huge gains in recent decades. Wheat and barley have also performed well.
As the chart shows, crops like sorghum and millet have lagged behind. A hectare of land could yield 5 to 6 tonnes of corn or rice but only 1 to 1.5 tonnes of millet and sorghum.
It’s not just that yields for these crops are much lower today; growth over the past 60 years has been much more modest, increasing by less than 50%.
This is a huge challenge since these are key staple crops across much of Sub-Saharan Africa, where hunger rates are the highest and farmer incomes are the lowest.
Read more in my article on increasing yields in Sub-Saharan Africa →
March 13
Government spending on health has grown substantially across rich nations since 1990, with particularly steep increases in the United States. The chart shows healthcare spending as a share of gross domestic product (GDP) in four countries.
Japan and the UK saw their share more than double, while it more than tripled in the United States, from 4.5% to 16% of GDP. The rising costs partly reflect demographic change, as older populations typically need more medical care, as well as the COVID-19 pandemic.
Each country organizes healthcare differently. Germany requires everyone to buy insurance from regulated providers, while Japan gives everyone government insurance. The United Kingdom provides healthcare directly through its national health service, while the US combines private insurance with government coverage for the elderly and those on low incomes.
Explore government health spending for more countries →
March 12
In 2000, Sierra Leone had the highest rate of maternal mortality in the world (alongside South Sudan). Around 1,800 pregnant women died for every 100,000 live births.
Since then, risks for mothers have plummeted. The country has focused on expanding healthcare, increasing the retention of skilled medical staff, and improving access to crucial medicines and treatments. In 2010, it rolled out free healthcare to pregnant women and children.
The results are shown in the chart. Maternal mortality rates have fallen by 74% in two decades.
While these rates are still extremely high — rates in the safest countries are around 100 times lower — Sierra Leone has made massive strides in saving both women and children.
Explore more global data on maternal deaths and declines over time →
March 11
In 1981, the major foreign aid donor countries, also known as the Development Assistance Committee, made a promise at the UN: to aim for at least 0.15% of their national income to assist the world's least developed countries — about 1 dollar out of 700.
Over the years, they repeated this pledge. But by 2022, most countries failed to honor this promise. The chart shows the 20 OECD countries giving the most aid, as a percentage of their national income, to the world’s poorest nations.
Only three countries met the target: Luxembourg, Sweden, and Norway.
Some countries are so wealthy that even a rounding error in their budgets could mean the difference between life and death for people in the poorest parts of the world.
Explore foreign aid given to least-developed countries for all donor countries →
