In this paper, we provide evidence that the time-series properties of stock returns includeboth structural change and time dependence in the conditional variance. The absence of astructural change component tends to overstate the persistence parameter in a time-dependentmodel specification. The...

By using an extensive dataset of more than 32 million messages on 91 firms posted on the Yahoo! Finance message board over the period January 2005 to December 2010, we examine whether investor sentiment as expressed in posted messages has predictive power for stock returns, volatility, and...