What Is an Insider Cluster Buy?
When one director buys shares of their own company, that is a data point. When three or four different insiders buy the same stock within a month, people start to pay attention. That pattern is called a cluster buy.
The definition used here
On Filed Trades a cluster buy is a stock where at least three different insiders made open market purchases within a 30 day window. Insiders are the officers, directors and large shareholders who must report trades to the SEC on Form 4, usually within two business days. The site records 21 open market insider trades and 40 scored clusters as of 2026-09-28 (28 September 2026).
Why buys are different from sales
Insiders sell for many reasons that say little about the stock. They pay taxes, buy a house, diversify a concentrated holding, or follow a plan set months earlier. They usually buy for one reason: they expect the shares to be worth more. That is why this site scores buys and shows sales without scoring them.
A cluster adds a second layer. Several people with different roles and different views of the business chose to put their own money in at about the same time.
Open market or not
Not every insider transaction is a purchase decision. Option exercises and stock awards are part of pay. Proposed sales are notices, not trades. Only open market buys and sales are counted here, because those are the ones that involve a choice about price.
When does the clock start
A cluster is not fully public until its last filing. So the return for a cluster on this site starts on the first trading day after the last filing in the group, the moment you could have known about all of it. Starting earlier would credit a follower with knowledge they did not have.
What the evidence can and cannot say
Clusters are rare, so the sample is small, and small samples give wide error bars. The performance page shows the cluster result at 30, 90 and 180 days with its sample size and a plain reading of the t statistic. If the result is not clearly different from the market, the page says so.
Even a real average edge would not make any single cluster a good buy. Some clusters fall. Insiders are wrong often, and they also know their company better than you do.
How to use the cluster list
Treat it as a place to start reading, not a list of tickers to copy. Open the stock page, look at who bought, how large the purchases were compared with their pay and holdings, and how the filings were spread over the window. See the full list on the cluster buys page.
This is information, not investment advice.