Peter Lynch said it best: "Insiders might sell their shares for any number of reasons, but they buy them for only one: they think the price will rise."
SafetyMargin.io tracks both insider buying and selling for every stock. Here's how to read the signals — and when to ignore them.
Insider Buying — The Strongest Signal
When a CEO, CFO, or board member spends their own money buying shares on the open market, they're putting real skin in the game. Unlike stock options or grants (which are free), open market purchases require writing a check.
What makes a buy signal strong?
Cluster buying — When multiple insiders buy within the same period, it's a stronger signal than a single purchase. If the CEO, CFO, and two directors all buy within the same quarter, they likely have a shared conviction about the company's prospects.
Size matters — A $50,000 purchase by someone earning $5 million is a rounding error. A $2 million purchase is a statement. Look at the dollar value relative to the insider's likely compensation.
Timing around bad news — When insiders buy after a significant stock price decline or negative earnings, they're signaling that the market has overreacted. This is the most contrarian — and often most profitable — insider signal.
C-suite vs. directors — Purchases by the CEO and CFO carry more weight than purchases by independent directors. Operating executives have the deepest understanding of the business trajectory.
What to look for on SafetyMargin.io
- Buys (3M) — Recent purchases are more relevant than old ones. A spike here is worth investigating.
- Buys (12M) — The longer-term context. Some companies have cultures of insider ownership; others rarely see open market purchases.
- Total value (12M) — The aggregate dollar amount. Large values amplify the signal.
- Individual transactions — Check who's buying, when, and at what price. Multiple names over multiple dates is the strongest pattern.
Insider Selling — More Nuance Required
Insider selling is not a reliable bearish signal by itself. Insiders sell for many legitimate reasons that have nothing to do with the company's prospects:
Why insiders sell (besides bearish conviction)
- Diversification — Having 80% of your net worth in one stock is risky. Financial advisors routinely recommend selling to diversify.
- Tax obligations — Stock option exercises trigger large tax bills that need funding.
- Life events — Buying a house, funding a trust, paying for education, or going through a divorce.
- Pre-planned sales (10b5-1 plans) — Many insiders set up automatic selling programs months in advance. These sales have zero information content. SafetyMargin.io excludes planned 10b5-1 sales from the selling activity to reduce noise.
- SBC dilution offset — In tech companies, insiders receive large stock grants annually. Selling some shares is simply taking compensation in cash form.
When selling IS a warning sign
Cluster selling at the top — When multiple insiders sell large amounts near all-time highs, especially outside of 10b5-1 plans, pay attention.
Unusual acceleration — An insider who normally sells $500K per quarter suddenly selling $5M is more informative than the steady seller.
Selling into strength before earnings — If insiders significantly increase sales in the weeks before an earnings report, they may know something the market doesn't.
What to look for on SafetyMargin.io
- Sells (3M) and (12M) — context for frequency
- Total value (12M) — watch for unusually large aggregate amounts
- Individual transactions — check the price, date, and relationship to earnings dates
Combining Buying and Selling Signals
The most informative scenario is when buying and selling tell the same story:
| Buying | Selling | Signal |
|---|---|---|
| High (cluster buys) | Low | Strongly bullish — insiders are loading up |
| None | Very high (cluster sells) | Worth investigating — but check for 10b5-1 plans |
| Moderate | Moderate | Neutral — normal insider activity |
| High buying + High selling | Mixed | Different insiders have different views; dig deeper |
Common Mistakes to Avoid
Overreacting to a single sale
One director selling shares is not a signal. It becomes meaningful only in aggregate — multiple insiders, large amounts, unusual timing.
Ignoring the base rate
In bull markets, insider selling increases naturally because stock prices are higher and compensation plans vest at higher values. Compare the selling activity to the company's historical pattern, not to an absolute standard.
Treating option exercises as purchases
SafetyMargin.io focuses on open market purchases — where insiders spend their own cash. Option exercises are not the same signal because the insider is merely converting existing compensation, not adding new capital at risk.
The Bottom Line
Insider buying is one of the most reliable signals in investing because the incentive alignment is clear: insiders buy with their own money when they believe the stock is undervalued. Insider selling requires more context and should rarely be used as a standalone sell signal.
On SafetyMargin.io, the Insider Buying and Selling sections give you the raw data to form your own judgment. Focus on cluster buying, large dollar amounts, and timing relative to price moves — and always consider the broader context before acting.