When there’s a general spirit of panic, the markets tend to fall by punctuated equilibrium. They’ll remain steady over months and then suddenly drop a great deal over a short period of time without warning.

It happened during the depression, and it’s also happening now. The decline has been fairly steady, but there have been days recently where the DJIA dropped 400+ points.

Still nothing on the scale of Black Tuesday. It would have to lose 20% of its value in a single day to exceed that.