Do Institutional Investor Cliques Undermine Stock Price Efficiency?

Abstract

This study investigates the effects of institutional investor cliques on stock price efficiency. Using a community network algorithm, it identifies cliques of institutional investors and finds that they significantly undermined stock price efficiency in China. The robustness of this finding is demonstrated through a range of methodologies, including the substitution of dependent variables, the alteration of estimation methods, the exclusion of data from extreme market periods, and the application of instrumental variables. The role of institutional investor cliques in diminishing market efficiency is attributed to market speculation. The detrimental effect of cliques on efficiency is exacerbated in environments characterized by low stock liquidity, poor information disclosure, and heightened panic among retail investors. However, regulatory interventions, such as inquiry letters, are shown to mitigate these effects and enhance market efficiency. These findings highlight the unexpected ways institutional investor cliques can influence emerging market economies and underscore the critical importance of effective regulation to safeguard market efficiency.