One type of cryptocurrency, a so-called stablecoin, is meant to keep its value at $1. But on 9 May, the third-biggest stablecoin, TerraUSD, fell as low as 69 cents, causing a flood of investors to sell their holdings.

Stablecoins get their name from their being tied to the value of government-issued currencies, such as the dollar. These $1 pegs are usually backed by Treasuries, cash and other dollar debt that is easily sold in times of market stress.