A group of 400 millionaires from 24 countries, including prominent names like Marvel actor Mark Ruffalo, musician Brian Eno, film producer Abigail Disney, physicist Brian Cox, and documentary filmmaker Abby Disney, have signed an open letter to world leaders at Davos calling on them to “tax the super-rich.” The letter urges elected representatives at the World Economic Forum (WEF) in Davos, Switzerland, to tackle the existential global crisis posed by extreme wealth.