It's called population momentum: when very large cohorts of young people reach childbearing age, the total number of births stays high even if each couple has fewer children. According to the UN, about two-thirds of the population increase expected by 2050 would happen even if fertility dropped immediately to around two children per woman everywhere. A population's past weighs on its future for a long time.
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.