What is cluster buying?
Cluster buying means that several insiders of the same company buy its shares within a short period. On this site a cluster starts at three different buyers who each reported an open-market purchase within 90 days.
The idea
One manager who buys shares is one decision. When a director, the CFO and a board member of the same company each buy within a few weeks, that is several people with their own money on the same side. Neither EU nor US law defines a cluster. It is a way of counting filings, and each source that uses the term picks its own window and minimum.
How this site counts a cluster
- Only open-market purchases count. Grants, option exercises and gifts do not.
- The window is 90 days and rolls: for each filing day the count looks back 90 days, up to and including that day.
- The date is the day the filing reached the regulator or the SEC, not the day of the trade.
- A company and a filing day appear in the list once the count reaches three buyers.
Who counts as one buyer
In the EU a manager reports their own trades and those of persons closely associated with them, such as a spouse or a holding company (what is a PDMR?). Counting each of them as a buyer would turn one family into a cluster.
- Dutch register: a person and the companies they file through count as one buyer. A buyer who only files as a legal entity counts as half. Three people and one such entity make 3.5.
- Swedish register: FI names the manager behind each filing by a closely associated person, so a spouse or holding company counts as that manager.
- German, Belgian and Spanish registers and US Form 4: the filings do not link these persons, so each filer counts once. A US filer is one SEC filer number.
What a cluster does not tell you
A cluster is a count of filings. Two buyers in 90 days do not appear, and neither does a company where the buys lie 91 days apart. Insiders can buy at the same time for one shared reason, such as the end of a closed period after results, when the trading window opens for all managers at once.
Clusters on this site
Buyer clusters lists the clusters across the six registers, newest filing date first, with the count of buyers for each. The underlying filings are all in Insider Trades, and the rules for who counts as one buyer are on the methodology page.
Checked against the regulation and the regulator’s own pages on Oct 31, 2026. This guide explains the rules; it is not legal or investment advice.
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