Information diffuses gradually within industries, from big firms to small ones. The past returns of large firms in an industry predict the future returns of small firms in the same industry — a within-industry lead-lag effect. Much of what looks like firm-level momentum is really the slow diffusion of industry-common information from leaders to laggards.
What anomaly it documents
Predictor: lagged returns of big firms in a stock's own industry.
Direction: positive — small firms follow their industry's big firms with a lag.
Shape: lead-lag concentrated within industry; subsumes part of momentum.
OSAP predictor: IndRetBig (big-firm industry return).
How to construct it
Sorting variable: prior-month value-weighted return of large firms in the same industry.
Universe: NYSE/AMEX/Nasdaq common stocks, grouped by industry.
Portfolio formation: rank small firms by their industry's big-firm lagged return.
Long / short: long stocks whose industry leaders rose, short those whose leaders fell.
Weighting: equal-weighted.
Rebalancing: monthly.
Evidence and replication
Period
Notes
Source
IS (1963–2001)
big-firm industry returns lead small-firm returns
this paper
OOS (post-2007)
gradual-diffusion lead-lag effects persist
post-publication
OSAP (IndRetBig)
replicates
Chen & Zimmermann 2022
Why it might work
Gradual information diffusion: investors specialize, so industry-common news reaches small/peripheral firms slowly.
Limited attention: small firms are under-monitored relative to industry leaders.
Limitations and risks
Momentum overlap: related to industry momentum and firm momentum.
High turnover: monthly reranking on lead signals is trade-intensive.
Microstructure: small-firm leg suffers illiquidity and stale prices.
Key references
Hou, K. (2007) — Industry Information Diffusion and the Lead-Lag Effect in Stock Returns — RFS — DOI: 10.1093/revfin/hhm003
Moskowitz, T. & Grinblatt, M. (1999) — Do Industries Explain Momentum? — JF
Provenance: generated from the paper's abstract and metadata, not full text; sample periods and replication notes are indicative — verify against the source.
