The Core Asymmetry
Insiders (executives, directors, 10%+ shareholders) sell for many reasons: taxes, diversification, house purchases, divorce, option vesting. Most insider selling is noise.
Insiders buy for one reason: they think the stock will go up. Peter Lynch put it well: "Insiders might sell their shares for any number of reasons, but they buy them for only one: they think the price will rise."
What Form 4 Actually Reports
Form 4 filings with the SEC must be submitted within two business days of an insider transaction. They disclose:
- Reporting person name and role
- Number of shares bought or sold
- Average price
- Shares held after the transaction
- Type of transaction (open market, option exercise, gift, etc.)
What Counts as a Strong Buy Signal
Open market purchases (transaction code "P")
- Insiders buying at market with personal cash. Strongest signal.
Cluster buying
- Multiple insiders (CEO, CFO, board members) buying within the same window. Suggests coordinated confidence.
Size relative to net worth
- A $500K purchase means more from a CFO with $2M net worth than a billionaire founder.
After recent weakness
- Insider buying into a 30%+ drawdown often marks capitulation lows historically.
What Doesn't Count
Option exercises (code "M")
- Not an open-market purchase. The insider is just converting vested options.
Shares retained after vesting
- Not a buy. Just not selling a vest.
10b5-1 plan sales
- Pre-programmed sales. No information content either way.
Small buys from large insiders
- A $50K buy from a billionaire CEO is noise.
Famous Insider Buy Examples
- Warren Buffett, Bank of America 2011: Bought $5B in preferred + warrants at the bottom. Became one of his best trades.
- Bill Ackman, Howard Hughes Corp: Repeated insider-style purchases signaled long-term conviction.
- Jamie Dimon, JPMorgan 2020: Bought $25M of JPM after pandemic crash. Stock doubled within 18 months.
Tracking Tools
- Free: SEC Edgar (searchable), OpenInsider.com aggregator
- Paid: Verity, Washington Service
- Real-time alerts: use Catalayer's [/monitor](/monitor) with keyword
insider buyingand your watchlist tickers
Using Insider Data in Screens
Build a screen combining:
- Net insider buying over last 6 months
- Stock down 20%+ from 52-week high
- Forward P/E below sector median
- Positive free cash flow
This blends insider signal with quantitative value.
Key Takeaways
- Insider buying is a stronger signal than insider selling
- Open-market purchases (code "P") are what matter
- Cluster buys from multiple insiders are strongest
- Size relative to insider net worth matters
- Combine with fundamental screens for best results
Track insider-related coverage across your watchlist at [/monitor](/monitor).