Building a Stock Linkage Factor from Mutual Fund Co-Ownership

Summary

This report explores whether stocks held together by investment funds form a useful relationship network. It offers two explanations: shared holdings may reflect common traits recognized by fund managers, and co-owned stocks may respond similarly because they share investors. The reported analysis finds higher linkage measures among stocks in the same industry, while the measures show no significant exposure to market capitalization across five size groups.

The report turns the network into a traction factor, based on the idea that a stock may catch up when its linked stocks have risen but its own return has lagged. In a historical test with monthly rebalancing and stated trading costs, the factor showed positive rank information coefficients and differentiated five portfolio groups. The document also reports results across broad market universes and major Chinese indices, with weaker performance and coverage in narrower or smaller-stock universes. These are historical findings over a limited sample; the report warns that future market conditions may change, and the summary does not provide enough detail to independently assess construction choices or robustness.

Key ideas

• Mutual funds' shared holdings are used to define links between stocks.
• The report interprets co-ownership as both a sign of common manager beliefs and overlapping shareholder bases.
• Linked-stock measures are higher for same-industry pairs, while showing no significant size exposure.
• The Traction20d factor seeks catch-up returns when linked stocks rise ahead of a stock itself.
• Historical portfolio tests report positive factor results, but do not establish future performance.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.