You might picture wads of small bills, but since 2017 there have been more $100 notes in circulation than $1 notes, according to the Federal Reserve. By the end of 2025, there were nearly 20 billion of them. These big bills are rarely used for everyday shopping: they are mostly hoarded, and a large share is thought to be held outside the United States, where the dollar serves as a safe store of value.
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.