The Small World of Investing: Board Connections and Mutual Fund Returns
Executive Summary — How does information flow in security markets, and how do investors receive information? In the context of information flow, social networks allow a piece of information to flow along a network often in predictable paths. HBS professors Lauren Cohen and Christopher Malloy, along with University of Chicago colleague Andrea Frazzini, studied a type of dissemination through social networks tied to educational institutions, examining the information flow between mutual fund portfolio managers and senior officers of publicly traded companies. They then tested predictions on the portfolio allocations and returns earned by mutual fund managers on securities within and outside their networks. Key concepts include:
- Social networks are important for information flow between firms and investors.
- Across the spectrum of U.S. mutual fund portfolio managers, fund managers place larger concentrated bets on stocks they are connected to through their education network, and do significantly better on these holdings relative to non-connected holdings, and relative to connected firms they choose not to hold.
- A portfolio of connected stocks held by managers outperforms non-connected stocks by up to 8.4 percent per year. This connection is not driven by firm, fund, school, industry, or geographic location effects, nor by a subset of the school connections (e.g., Ivy League).
- The bulk of this premium occurs around corporate news events such as earnings announcements. This finding suggests that the excess return earned on connected stocks is driven by information flowing through the network.
- As the information will eventually be revealed into stock prices, advance knowledge implies return predictability.
This paper uses social networks to identify information transfer in security markets. We focus on connections between mutual fund managers and corporate board members via shared education networks. We find that portfolio managers place larger bets on firms they are connected to through their network, and perform significantly better on these holdings relative to their non-connected holdings. A replicating portfolio of connected stocks outperforms a replicating portfolio of non-connected stocks by up to 8.4% per year. Returns are concentrated around corporate news announcements, consistent with mutual fund managers gaining an informational advantage through the education networks. Our results suggest that social networks may be an important mechanism for information flow into asset prices.