What happens when an anonymous Twitter short-seller spreads completely unsourced news gathered from an equally anonymous alt-right terror-news aggregator that Gary Cohn is finally answering to a higher power and stepping down from his position as chief White House economics guy? Obviously, this:
The tweets in question, since deleted, were echoed elsewhere and racked up scores of retweets themselves. Otherwise sober-minded market observers openly speculated about Cohn's departure. Markets convulsed.
Then it was all revealed as bunkum and prices recovered – kind of – because markets are nothing if not a rational and efficient aggregation of all available information. Kind of.
Or maybe all those algos are just following the wrong Twitter accounts.