In 2010, Johan Bollen, an associate professor at Indiana University and two other professors published research showing how using Twitter could with more than 85% accuracy predict the daily up and down readings of the Dow.

WSJ: In the Wired World, Feeds Drive Trading

Dr. Bollen and his colleagues, for example, found that the millions of Twitter messages sent via mobile phones and computers every day captured swings in national mood that presaged changes in the Dow Jones index up to six days in advance with 87.6% accuracy.

WSJ: The Really Smart Phone