Fake News: Evidence from Financial Markets

Abstract

Using a unique dataset of fake paid-for articles obtained from an SEC investigation, we examine the impact of fake news in financial markets. In addition to the known fake articles, we use a linguistic algorithm to detect deception in expression for a much larger set of news content with unknown authenticity. The known fake articles are used to validate the algorithm. We find increases in abnormal trading volume and temporary price impact following fake news for small firms, but no impact for large firms. Following the SEC’s announced investigation, we find a marked decrease in the probability of false content and a decrease in reaction by investors to all news, but especially content with less authenticity. These findings are most pronounced for small firms with high retail ownership. Finally, small firms engage in press releases, 8-K filings, and insider trading that coincide with fake articles, consistent with concerns of coordinated stock price manipulation. No such patterns are observed for large firms. Our setting provides a unique opportunity to quantify fake news’ impact that avoids the joint hypothesis problem plaguing tests of informational efficiency.

Keywords: fake news, market efficiency, textual analysis

JEL Classification: G14