In the first essay titled "Shareholder Coordination, Information Diffusion and Stock Returns", we show that the quality of information sharing networks linking firms' institutional investors has stock return predictability implications. First, we demonstrate that firms with high shareholder coordination experience less local comovement and less post earnings announcement drift, consistent with the notion that coordination improves firms' information environment. We then document that the stock return performance of firms with high shareholder coordination leads that of firms with low shareholder coordination, supporting the view that coordination acts as an information diffusion channel. Finally, we provide evidence consistent with the notion that the market does not readily recognize the superior quality of high shareholder coordination firms and prices it gradually through the trading of sophisticated institutional investors, thereby causing future returns to be positively associated with shareholder coordination. In the second essay titled "Shareholder Coordination and Stock Price Informativeness", we find that stock prices of firms with better information sharing networks linking institutional shareholders exhibit higher levels of idiosyncratic volatility. This positive relation between shareholder coordination and stock price informativeness is mainly driven by coordination among dedicated and independent institutions and exists even after accounting for endogeneity. We further show that institutional trading serves as an information diffusion channel that strengthens the relationship of shareholder coordination with price informativeness. Overall, our results indicate that a higher degree of shareholder coordination leads to more informative stock prices by encouraging the collection of and trading on private information.