Prior research documents capital market benefits of increased investor attention to accounting disclosures and media coverage; however, little is known about how investors and markets respond to attention‐grabbing events that reveal little nonpublic information. We use daily firm advertising data to test how advertisements, which are designed to attract consumers' attention, influence investors' attention and financial markets (i.e., spillover effects). Exploiting the fact that firms often advertise at weekly intervals, we use an instrumental variables approach to provide evidence that print ads, especially in business publications, trigger temporary spikes in investor attention. We further find that trading volume and quoted dollar depths increase on days with ads in a business publication. We contribute to research on how management choices influence firms' information environments, determinants and consequences of investor attention, and consequences of advertising for financial markets.

We study sources of investor disagreement using sentiment of investors from a social media investing platform, combined with information on the users' investment approaches (e.g., technical, fundamental). We examine how much of overall disagreement is driven by different information sets versus differential interpretation of information by studying disagreement within and across investment approaches. Overall disagreement is evenly split between both sources of disagreement, but within‐group disagreement is more tightly related to trading volume than cross‐group disagreement. Although both sources of disagreement are important, our findings suggest that information differences are more important for trading than differences across market approaches.

Using high-frequency disagreement data from the investor social network StockTwits, we find that greater unsophisticated disagreement facilitates informed buying and selling. During periods of overvaluation, the facilitating effect of disagreement on trading is dampened for informed buyers but is amplified for informed sellers. These findings are unexplained by sentiment, news, and retail order flow, and they remain when we measure disagreement overnight and disagreement of technical investors, which alleviates the concern that disagreement and informed trading respond to a common shock. These findings suggest that informed traders respond meaningfully but differently to valuation changes induced by unsophisticated disagreement.

This paper studies whether social media sentiment predicts merger withdrawals. We find that a one‐standard‐deviation increase in social media sentiment after a merger announcement is associated with a 0.64 percentage point lower probability of withdrawal (16.6% of the average). This effect is unexplained by abnormal price reactions, traditional news, and analyst recommendations. Consistent with manager learning, the informativeness of social media strengthens after firms start corporate Twitter accounts. The informativeness is driven by longer acquisition‐related tweets by fundamental investors, rather than memes and price trend tweets. These findings suggest that social media signals can be important for corporate decisions.

We examine social media attention and sentiment from three major platforms: Twitter, StockTwits, and Seeking Alpha. We find that, even after controlling for firm disclosures and news, attention is highly correlated across platforms, but sentiment is not: its first principal component explains little more variation than purely idiosyncratic sentiment. Using market events, we attribute differences across platforms to differences in users (e.g., professionals versus novices) and differences in platform design (e.g., character limits in posts). We also find that sentiment and attention contain different return-relevant information. Sentiment predicts positive next-day returns, but attention predicts negative next-day returns. These results highlight the importance of considering both social media sentiment and attention, and of distinguishing between different investor social media platforms.