  By exploiting a bipartite network representation of the relationships between
mutual funds and portfolio holdings, we propose an indicator that we derive
from the analysis of the network, labelled the Average Commonality Coefficient
(ACC), which measures how frequently the assets in the fund portfolio are
present in the portfolios of the other funds of the market. This indicator
reflects the investment behavior of funds' managers as a function of the
popularity of the assets they held. We show that $ACC$ provides useful
information to discriminate between funds investing in niche markets and those
investing in more popular assets. More importantly, we find that $ACC$ is able
to provide indication on the performance of the funds. In particular, we find
that funds investing in less popular assets generally outperform those
investing in more popular financial instruments, even when correcting for
standard factors. Moreover, funds with a low $ACC$ have been less affected by
the 2007-08 global financial crisis, likely because less exposed to fire sales
spillovers.
