About 1.6 million sets of twins are born every year, and one baby in 42 is a twin. A study published in Human Reproduction in 2021, covering 165 countries, found that the twinning rate has risen by a third since the 1980s, from 9 to 12 per 1,000 deliveries. The main drivers are assisted reproduction and later motherhood, both of which make fraternal twins more likely. The rate of identical twins has stayed flat, at around 4 per 1,000.
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.