On the Importance of Text Analysis for Stock Price Prediction.

We investigate the importance of text analysis for stock price prediction. In particular, we introduce a system that forecasts companies' stock price changes (UP, DOWN, STAY) in response to financial events reported in 8-K documents. Our results indicate that using text boosts prediction accuracy over 1 0 % (relative) over a strong baseline that incorporates many financially-rooted features. This impact is most important in the short term (i.e., the next day after the financial event) but persists for up to five days.