This is Engel's law, set out by German statistician Ernst Engel in 1857 and confirmed around the world ever since. In the richest countries, households often spend less than 10-15% of their budget on food; in the poorest, the share frequently exceeds 40%. People spend more on food in absolute terms, but it weighs far less in the budget.
That's the estimate from a WHO-led study published in The Lancet in 2024, covering the half-century since the Expanded Programme on Immunization was launched in 1974. It works out to about six lives saved every minute, mostly infants. The measles vaccine alone accounts for around 60% of those lives.
According to the World Gold Council, about 216,000 tonnes of gold have been mined in all of human history. Because gold is so dense (19.3 tonnes per cubic metre), it would fit in a cube about 22 metres on each side, roughly the height of a seven-storey building. Strikingly, about two-thirds of it has been mined since 1950.