According to the UN, which harmonised its definitions in 2025, the world had 8 urban areas of more than 10 million people in 1975; today it has 33, 19 of them in Asia, and should reach 37 by 2050. Of the ten largest, only one lies outside Asia: Cairo. The planet's urban centre of gravity has shifted in just two generations.
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.