The Dow dropped 392 points on Thursday. The S&P 500 fell 2.4%, while the Nasdaq tumbled 3%.
The wave of selling has knocked the Dow down 911 points, or more than 5% so far this year. That's the worst four-day percentage loss to start a year on record, according to FactSet stats that go back to 1897. The Nasdaq, down over 6% in 2016, is off to its bleakest start since 2000.