The stock market experienced a significant decline, with some reports indicating it was the worst day since October or at least since April. The drop was attributed to threats of tariffs, possibly related to China or Greenland, although the specific target of the threats is unclear. The extent of the decline is also somewhat uncertain, with reports of the Dow dropping by as much as 800 points, but also a contradictory report of the Dow surging 550 points after the threats were allegedly backed off.