Peter Lynch famously said: "Insiders might sell their shares for any number of reasons, but they buy them for only one: they think the price will rise."
What Counts as Insider Buying?
"Insiders" include: CEO, CFO, COO, board members, and any shareholder owning >10% of the company. When they purchase shares on the open market with their own money (not stock options or grants), it's a powerful signal.
The Data Behind Insider Buying
Research by Nejat Seyhun (University of Michigan) found that stocks with heavy insider buying outperform the market by 8.9% per year on average.
| Signal | Average 12-Month Excess Return |
|---|---|
| CEO buys | +11.2% |
| Multiple insiders buy | +13.4% |
| Large purchase (>$500K) | +15.1% |
| Cluster buying (3+ insiders within 30 days) | +18.7% |
| Insider sells | -0.4% (nearly irrelevant) |
Key Takeaway: Insider selling is noise. Insider buying is signal.
How to Track Insider Activity
All insider transactions must be reported to the SEC within 2 business days via Form 4 filings. These are public records available on EDGAR.
The Insider Buying Checklist
- Is the purchase a direct open-market buy (not options exercise)?
- Is the purchase size meaningful (>$100K)?
- Are multiple insiders buying within a short timeframe?
- Is the buying happening after a stock price decline (contrarian signal)?
- Does the company have solid fundamentals to support recovery?
When Insider Buying Fails
Insiders aren't always right. They may buy to signal confidence during a PR crisis or to prevent a hostile takeover. Always cross-reference insider activity with fundamental analysis.
How Aristockrat Uses Insider Data
We aggregate Form 4 filings and calculate an "Insider Sentiment Score" for each stock. When insider buying coincides with a high Quality Score and low Valuation Score, that's what we call a "Triple Bullish Signal" — one of the strongest buy indicators in our system.