Markets dropped 53-56% in the 2007-2009 crash. Even a modestly well off investor like me can survive that if they take a hold position as Felix suggests. Selling is actually what hurts you because it converts your paper loss into a real one. I would feel it, but I would be fine in the long haul. Guys like Gates and Musk might just have to put off an acquisition or two for a few years. They'd still be incredibly wealthy. The people who get burned in a crash are people with modest means who threw their limited savings into a bull market without really understanding the implications of that bull market ending. People who understand markets or have advisors who do, which is most of not all of the Fortune listed billionaires and lot of people in the tier below that, will have strategies to deal with a crash.