Trader Brian Jones on Twitter: "20% drop from S&P 3380 takes us to around a drop of 680 S&P points or to around 2700. But this could be even worse than that at the speed it's moving." / Twitter

20% drop from S&P 3380 takes us to around a drop of 680 S&P points or to around 2700. But this could be even worse than that at the speed it's moving.