What is an insider cluster buy?

A cluster buy is when two or more distinct insiders — officers, directors, or 10% owners of the same company — each buy the company's stock on the open market within a short, rolling window. One insider buying can mean many things. Several insiders reaching the same conclusion independently, at the same time, with their own money, is a much harder signal to explain away.

Why clusters beat single buys

The academic literature on insider trading — from Cohen, Malloy & Pomorski's "Decoding Inside Information" to decades of earlier studies — keeps landing on the same two findings: purchases predict returns better than sales predict declines, and consensus purchases — multiple insiders buying together — outperform lone purchases. A single director's buy might be portfolio rebalancing, an optics purchase after a bad quarter, or a scheduled accumulation. When the CFO, a director, and a 10% owner all step in during the same short window, each of them is making an independent judgment from a different vantage point inside the same business.

What qualifies (our definition)

• Open-market purchases only — Form 4 transaction code P. Grants, option exercises, and 10b5-1 scheduled buys don't count. See Form 4 transaction codes.
• Two or more distinct insiders — same person filing twice is one insider, not a cluster.
• Within a rolling window — close enough in time that the buys reflect the same information environment.
• Any company size — we track clusters from micro-caps to mega-caps. The signal tends to run strongest in smaller names; see why small-cap insider buying matters.

Where to see live cluster buys

We parse every Form 4 as it hits SEC EDGAR and detect clusters continuously. Browse every stock with a detected cluster buy, see which insiders buy the most, or scan activity by sector.