Cluster insider buying
Why three insiders buying the same stock in the same window is the strongest pattern in Form 4 data, and how to read one properly.
The pattern
A cluster signal is what you have when three or more separate insiders at the same company file open-market buys (Code P) within a 60-day window. CatalystView tracks clusters on the buy side only — Code-S sells are noisier (taxes, 10b5-1 plans, diversification) and don't carry the same coordinated-conviction meaning. The classic academic work on cluster buying dates back to Seyhun (1986) and has been replicated many times: cluster buys tend to outperform single-insider buys and the broader market on a 30- to 90-day horizon.
Our threshold is three buyers because that's where the historical edge stops looking like noise. Two insiders buying could be a coincidence. Three is coordination of belief — all seeing the same thing, at the same time, and acting on it with their own money.
What makes a cluster strong
- Officer-heavy clusters. Two or three C-suite buyers (especially a CFO) carry more weight than a cluster of directors.
- Compressed timing. Three buys in two weeks is louder than three spread across 55 days — tight timing usually means a shared internal data point or board meeting.
- Substantial dollar size. Real money relative to each buyer's net worth is signal. Everyone buying the $5,000 minimum to satisfy a board rule is noise.
- Price near the 90-day low. Insiders buying near the bottom of a range is a strong setup; chasing momentum near a 90-day high is much weaker.
Common failure modes
- Forced ownership thresholds. New-director clusters in the first 90 days post-IPO or post-appointment often have no information content.
- 10b5-1 plan buys. Rare, but they happen — always check the footnote.
- Mega-cap clusters. A $250K cluster in a $500B mega-cap means little versus the same cluster at a $500M mid-cap. Size relative to market cap is what makes it usable.
How CatalystView handles clusters
Whenever a new Code-P filing lands, we look back 60 days for other open-market buys on the same ticker. If the cluster crosses the three-buyer threshold, the trade is routed to our deepest AI-analysis tier instead of the standard one, and the cluster member count is shown next to the signal on the feed and the stock page.
If the cluster grows after the first analysis — a fourth buyer joins, or the same buyers buy more — we re-run the analysis automatically and flag the change. See the methodology page for the full pipeline.