When company executives buy their own stock with own money, that's a strong bullish signal. Selling is weaker as a bearish signal (insiders sell for many non-information reasons).
Seyhun 1998 (the canonical text on insider trading): open-market purchases by officers and directors predict positive abnormal returns. We pull SEC Form 4 filings, weight by transaction size, scale by company market cap. Score uses net dollar flow over rolling 90-day window — insider purchases push score up, sales push it down.