"Investors have started the new year in panic mode," Ed Yardeni, president of investment advisory Yardeni Research, told CNN Money.
On the morning of January 4, the Dow dropped by 450 points, or 2.5 percent. The S&P 500 dropped by 2.1 percent.
According to Bloomberg, the biggest drop in the first trading day of the year – by 6.9 percent – was seen in 1932, during the Great Depression. In 2001, the Dow plunged by 2.8 percent as part of the dot-com collapse crisis.