Using hand-collected data, we find that activist shareholders often publicly disclose open letters that demand various changes in corporate operating decisions at their target firms. These letters are associated with significant stock price movements, decreased bid-ask spreads, and key activism outcomes such as directorship wins, corporate strategy shifts, and proxy advisor recommendations. Managers commonly respond to activists' open letters with their own voluntary disclosures. We conclude that activists use voluntary disclosure to mitigate investor information asymmetry and that managers' voluntary disclosures can be induced by activists
