A CEO buying their own stock is a signal. A CEO, CFO, and COO all buying the same stock within the same week is a different kind of signal entirely. In insider trading research, this pattern is called cluster buying, and it produces the strongest forward returns of any insider activity category.
What qualifies as cluster buying
There's no official SEC definition. In academic literature and most screening tools, cluster buying is typically defined as three or more insiders purchasing open-market shares of the same company within a 14-day window. Some researchers use a 7-day window for a tighter filter.
The key constraints:
- Must be open-market purchases (transaction code "P") — not options exercises, grants, or plan-based buys
- Must be different individuals — one person buying on three separate days doesn't count
- Must be C-level or director-level insiders — 10% holders buying together may reflect coordinated fund activity, not company-level conviction
A single insider might buy for personal reasons — portfolio rebalancing, tax planning, compensation diversification. When three or more executives independently decide to deploy personal capital into their own stock within the same window, the probability that it's coincidental drops sharply. They're all seeing the same internal data and reaching the same conclusion.
The academic evidence
Multiple studies have examined cluster insider buying. The results are consistent:
Cluster buys outperform single-insider purchases by roughly 5 percentage points on average. The effect is amplified in small and mid-cap companies where information asymmetry is higher.
Case study: Hamilton Lane (HLNE) — February 2026
On February 20, 2026, three executives at Hamilton Lane filed Form 4 disclosures for open-market purchases — all on the same day:
| Date | Insider | Title | Shares | Price | Value |
|---|---|---|---|---|---|
| Feb 20 | Juan Delgado-Moreira | Co-CEO | 9,225 | $107.10 | $989,311 |
| Feb 20 | Erik Hirsch | Co-CEO | 9,225 | $107.13 | $988,260 |
| Feb 20 | Andrea Kramer | COO | 2,325 | $107.53 | $250,011 |
Total cluster value: $2,227,582 across three executives on the same day.
Hamilton Lane is a leading global private markets investment firm. The stock had lost approximately 20% in the four weeks prior to these purchases, creating a notable discount from recent trading levels. The cluster buy came shortly after the company's Q3 fiscal year 2026 earnings report.
What the executives likely saw
Three C-suite officers buying on the exact same day during a 20% drawdown suggests coordinated conviction — not in the illegal sense, but in the sense that all three independently evaluated the same internal data and reached the same conclusion at the same time. Possible factors:
- Q3 earnings data suggesting the stock decline was overblown relative to fundamentals
- Pipeline visibility into upcoming fund closings or fee revenue that the market hadn't priced in
- Awareness that the 20% pullback created a rare entry point for a company with Hamilton Lane's growth profile
- Confidence in the private markets industry trajectory that outside investors were discounting too heavily
Co-CEO Delgado-Moreira's purchase is particularly notable because he had a documented history of previous buying, including a purchase in November 2025 at higher prices. Buying again at a lower price demonstrates averaging down with conviction — the opposite of what you'd see from someone losing confidence in the business.
Our algorithm scored the COO's signal at 73.2/100, with the Co-CEOs scoring 71.2 and 67.0 respectively. The cluster collectively shows strong fundamental and financial profiles (85/80 on the top signal), with the lower technical score reflecting the stock's recent downtrend — which is precisely the condition that created the buying opportunity.
View COO SEC filing · View Co-CEO Delgado-Moreira SEC filing · View Co-CEO Hirsch SEC filing
Second cluster: RLI Corp (RLI) — January 2026
Hamilton Lane isn't the only cluster event we tracked in Q1 2026. On January 23, 2026, two executives at RLI Corp also bought on the same day:
| Date | Insider | Title | Value |
|---|---|---|---|
| Jan 23 | Craig Kliethermes | CEO | $287,250 |
| Jan 23 | Jennifer Klobnak | COO | $115,980 |
Total cluster value: $403,230 across two executives on the same day.
RLI is a specialty insurance company with 30 consecutive years of underwriting profits and an AM Best A++ rating — the highest possible. Both purchases came right after a strong Q4 earnings beat. While this is a two-person rather than three-person cluster (making it a CEO+CFO pair pattern in the academic framework), the timing — same day, immediately post-earnings — and the quality of the underlying company make it a compelling signal. Our algorithm scored the CEO's purchase at 72.4/100, with fundamental and financial scores of 90 and 95 respectively.
How to screen for cluster buying
If you're tracking insider purchases manually, here's a practical screening method:
- Start with your purchase list. Filter all Form 4 filings for open-market purchases (code "P") by officers and directors.
- Group by company and date range. For each company, check whether multiple filings occurred within a 14-day window.
- Count unique insiders. Same person buying multiple times is repeat buying (still a signal, but weaker). You want three or more different people.
- Verify roles. CEO + CFO + COO is stronger than three independent directors. Weight the signal by how close the buyers are to company operations.
This is labor-intensive to do manually, which is one reason cluster signals are under-followed — they require cross-referencing multiple filings rather than reading individual ones.
When cluster buying doesn't work
Not all cluster events are equal. Watch for these diluters:
- Micro-cap token purchases. If three executives each buy $10K of a $50M market cap company, it might be a symbolic gesture or board requirement rather than conviction.
- Post-IPO purchases. Insider buying shortly after an IPO sometimes reflects lock-up optics rather than value assessment.
- Simultaneous with share issuance. If the company is issuing new shares or convertible debt while insiders buy, the signal is diluted.
- Regulatory or governance-driven. Some companies have minimum ownership requirements for executives. Check whether the purchase brings the insider up to a mandated threshold.
Neither the Hamilton Lane nor the RLI cluster triggers these red flags. The HLNE cluster totals $2.2M across three senior executives at a company with no concurrent share issuance — this is conviction capital, not optics. The RLI cluster pairs the CEO and COO at a blue-chip insurance company buying right after earnings confirmation.
The takeaway
Cluster buying is rare — it occurs in roughly 2–3% of companies per quarter. That rarity is part of what makes it valuable. When multiple C-level executives independently deploy personal capital into the same stock within the same window, they're expressing a level of collective conviction that no analyst report or earnings call can replicate.
The Hamilton Lane case is particularly instructive: $2.2M across three executives, all on the same day, during a 20% drawdown, shortly after an earnings report. That's the anatomy of a high-conviction cluster event. And when a second cluster at RLI Corp echoes the same pattern — CEO and COO buying on the same day right after earnings — it reinforces the thesis that Q1 2026 was a quarter where C-suite insiders were stepping up with real money while the market hesitated.
If you're only tracking one insider signal pattern, this is the one to prioritize.