In 1648, a Dutch water authority in charge of dikes, the Lekdijk Bovendams, borrowed money to pay for repairs. It issued a perpetual bond: with no repayment date, it pays interest forever. Yale University acquired one of these bonds in 2003. In 2015, Yale claimed twelve years of back interest and received about 136 euros. More than three and a half centuries on, the body that succeeded the original issuer still honours the debt.
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.