There is an old line that insiders sell for many reasons but buy for only one. It is a simplification, but a useful one. When the people who run a company put their own money into its stock, it is worth paying attention.
Insider transactions are disclosed in the US through Form 4 filings, and on their own each one is just a data point. Aggregated and read carefully, they become one of the more honest signals available, because they show what informed people do rather than what they say.
Why buying is the signal that matters
Insiders sell for all sorts of innocent reasons: diversification, a tax bill, a house, a divorce. A sale tells you little about their view of the business. A purchase is different. An executive buying shares in their own company, with their own money, at market prices, is making a deliberate bet on a business they understand better than any outside analyst ever could. It is the one transaction that is genuinely hard to explain away.
But not all buys are equal
The craft is in separating meaningful buying from noise. A purchase funded by exercising options is not the same as an executive reaching into their own pocket. Size relative to the person’s wealth matters: a token buy by a wealthy CEO is often just optics, while a large discretionary purchase is a real statement. So does the role. A chief financial officer buying tends to carry more weight than a non-executive director, simply because of what they can see.
The power of clusters
The strongest version of the signal is rarely a single buyer. It is a cluster: several insiders at the same company independently buying over a short window. One person can be wrong, early or idiosyncratic. When the CEO, the CFO and two directors all buy within a few weeks, the odds that they are collectively seeing something the market has missed rise considerably. Clusters of buying have historically tended to precede periods of outperformance more reliably than any individual transaction.
Beyond the corporate suite
The same lens extends to policymakers. Disclosure rules mean the trading of certain public officials is also a matter of record, and while the motivations are more debated, the transparency is real. Read as a dataset rather than a headline, this activity is simply another set of informed participants revealing their positioning.
Reading it honestly
None of this is a crystal ball. Insiders can be wrong, early, or buying out of confidence rather than information. The signal works best as one input among many, a way to sharpen conviction rather than replace analysis. Treated that way, with attention to who is buying, how much, and alongside whom, insider activity is a quietly powerful complement to fundamental work.
Our insider tools are built to make that reading easy: aggregating Form 4 activity across corporate insiders and policymakers, surfacing the clusters, and separating the meaningful purchases from the routine, so the signal is visible without the noise.