Cluster buys — what they are and why they matter
When multiple insiders at the same company buy in the same week.
A cluster buy is when three or more distinct insiders at the same company disclose buys within a short time window — typically a week.
Why it matters: one insider buying could be a one-off. Two within a week could be coincidence. Three or more is rarely random — it usually signals that internal information is widely circulating in the C-suite and that the senior team consensus is "the stock is cheap".
Research backing: studies of US insider data show cluster buys outperform isolated buys by a factor of 1.5-2x on subsequent 3-month returns.
Confounders to watch for:
- Compensation events. Some companies have coordinated windows where RSUs vest and executives receive shares on the same day. Those aren't really "buys" — they're award-based transfers. Filter by transaction type (Kauf/Purchase) to exclude.
- Rights issues. When a company issues new shares at a discount, insiders often subscribe as a group. Signal is weaker because they'd be diluted if they didn't participate.
- Loyalty programs / mandated holdings. Some boards require directors to hold X% of their compensation as stock. Regular buying to meet that target is mechanical, not directional.
InsideREU's /cluster page filters to genuine distinct buys across unrelated reporters — you can see the list of buyers to sanity-check whether it's a real cluster or a compensation event.