We study the observability of investors’ information-acquisition activities in financial markets. Improving observability leads to two strategic effects on information acquisition: (1) the pricing effect, which arises from interactions between investors and the market maker and can encourage or discourage information acquisition, and (2) the competition effect, which concerns interactions among investors and always encourages information acquisition. We apply our theory to study voluntary and mandatory disclosures of corporate site visits. When the competition effect dominates, investors voluntarily disclose their visits. When the pricing effect dominates, mandatory disclosure is effective. Our analysis sheds novel light on Regulation Fair Disclosure.

We study voluntary cost disclosure by duopoly firms when they can invest in a cost-reduction technology, i.e., when their private cost is endogenously determined. We find that, contrary to most of the literature, firms disclose their endogenous cost information regardless of the type of competition. The underlying mechanisms and welfare implications, however, are different. Under Bertrand competition, cost disclosure helps a firm avoid aggressive investment in cost reduction to coordinate actions to the mutual advantage of the duopoly firms. Under Cournot competition, disclosing cost information enables a firm to show a hardened stance toward the competing firm. Although firms gain from their disclosure decisions under Bertrand competition, their disclosure decisions under Cournot competition place them in a prisoner’s dilemma, as both firms would be better off if they chose not to disclose their information. Consequently, consumers may lose under Bertrand competition but gain under Cournot competition.

We study information sharing between strategic investors who are informed about asset fundamentals. We demonstrate that a coarsely informed investor optimally chooses to share information if his counterparty investor is well informed. By doing so, the coarsely informed investor invites the other investor to trade against his information, thereby reducing his price impact. Paradoxically, the well informed investor loses from receiving information because of the resulting worsened market liquidity and the more aggressive trading by the coarsely informed investor. Our analysis sheds light on phenomena such as private communications among investors and public information sharing on social media.