Cluster buys: when three or more insiders buy the same stock

GuideNumbers as of 2026-10-14

One insider buying can mean anything. Three insiders independently buying the same stock in the same few weeks means several people with inside knowledge decided, separately, that the price was wrong. That coincidence is the strongest single pattern in insider filings, and the Cluster Buys page finds every instance of it.

The definition

A cluster is a window of no more than 60 days in which three or more distinct insiders bought the same company's stock on the open market. The members page currently lists 1,489 of them since 2024-10-01, newest, largest or best-scored first, with filters for buyer count, officers-only, CEO/CFO/chair involvement and recency.

The score, out of 100

Buyers, up to 50. Three buyers is the floor; six or more is the ceiling. More independent decisions, more weight.
Who, up to 15. Officers and directors over 10% holders and funds. A CEO, CFO or chair among the buyers lifts it further.
Size, up to 25. Dollars bought relative to the company, so a $2M cluster at a micro-cap outranks a $2M cluster at a mega-cap.
Conviction, up to 10. Buying at least 25% below the recent high, first-ever purchases, or an insider's largest purchase on record.
Offering penalty. Buying tied to a public offering or a private placement is a real filing, correctly coded P, but it is not several people independently choosing to buy on the open market. It is marked and scored down.

Why it matters

In the historical event study, purchases that were part of a cluster ran ahead of single purchases on a market-adjusted basis over the following quarter, in both the training years and the holdout years after 2022. It is an average tilt with wide dispersion — plenty of clusters are followed by falls — so the page shows the chart, the price move since the window and every buyer, and lets you judge.

Every Tuesday the blog posts the ten strongest clusters of the last six weeks for free. Members see all of them, and can have an email the morning a new cluster scores 55 or more.

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Questions this post answers

What is an insider cluster buy?

Three or more distinct insiders buying the same company's stock on the open market within a window of no more than 60 days.

How is the cluster score calculated?

Up to 50 points for the number of buyers, 15 for who they are, 25 for dollar size relative to the company, 10 for conviction signals, minus a penalty when the buying is tied to an offering or placement.

Do cluster buys beat the market?

On average, in the historical study, cluster purchases ran ahead of single purchases over the following quarter, in both the pre-2022 and holdout years. Average tilt, wide dispersion, not a forecast.

Can I get alerted when a cluster forms?

Yes. Members can switch on a market-wide cluster alert (score 55+) and receive one email the morning after the filing that completed the window lands.

Are clusters available through the API?

Yes. GET /api/v1/clusters with optional ticker, min_score, since and limit parameters returns the same scored list as the page.

Members Cluster Buys page Email alerts guide The Filings Browser The Trader Atlas The Backtest engine Seasonal stock patterns that survived an out-of-sample test Chart formations

Built from SEC EDGAR ownership filings. Only open-market purchases (transaction code P) and sales of $1M or more are counted; grants, option exercises and tax withholding are excluded because they run on schedules set years earlier. Historical description, not a prediction, and not investment advice.