The Insider Buying Index

Insider buying vs the market

The S&P 500 (top) plotted over the same weeks as insider buying pressure (bottom), so you can see how the two move together. Each buying point is one week's share of insider dollars that went to buying rather than selling, smoothed over three weeks. Watch whether insiders lean in before the market rises, or pull back before it turns.

The dashed line marks weeks where insiders bought and sold equal dollar amounts. Above it, buying dominates.

What it means

Insiders sell for many reasons but tend to buy for only one: they think the stock is cheap. The index reads the whole market at once, so a high number means an unusually large share of insider money is flowing into open-market purchases right now, and a low number means insiders are mostly sitting on their hands. It is a market-wide temperature gauge, not a call on any single stock, and like every insider signal it works best as one input among several.

How it is calculated

We take every open-market purchase (SEC Form 4, code P) and open-market sale of $10K or more across the US market over the last five years and group them by week. For each week we measure buying as a share of total insider dollars, buys divided by buys plus sells, then smooth it over three weeks to cut noise and rank the latest completed week against every week since 2021. The result is a 0 to 100 percentile: 100 is the heaviest insider buying in five years, 0 the lightest. It refreshes on its own as new filings arrive. This is a descriptive market indicator, not investment advice.