Using a new measurement method published in late 2025, the UN now ranks Jakarta first, with nearly 42 million people, ahead of Dhaka (almost 40 million) and Tokyo (33 million). Tokyo hasn't emptied out: what changed is how the boundaries of urban areas are drawn. By 2050, Dhaka could become the largest city on Earth.
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.