What is a 'herd signal' in congressional trading?
When several lawmakers pile into the same stock at once — and why that's worth noticing.
A herd signal is what Congress Watch calls it when several members of Congress buy or sell the same stock within a short window. It is one of the most useful patterns in the disclosure data.
Why a cluster matters more than one trade
A single lawmaker buying a stock is noise. But when five, six, or seven members independently move into the same company in the same few weeks, that cluster is harder to dismiss as coincidence — and it tends to be the kind of thing readers and markets pay attention to.
What we actually measure
A herd signal is a descriptive statistic, not an accusation. For each cluster we look at:
- How many members traded the stock.
- The direction — were they mostly buying or selling?
- The tightness of the window — days, not months.
We do not claim the members coordinated or acted on inside information. We report the pattern; you draw your own conclusions. See Methodology for the precise definition.
See it in action
Browse the most-traded stocks to see where the herd is gathering, or read our latest coverage for the day's strongest cluster.
Public disclosures — not financial advice.
Does a herd signal mean lawmakers coordinated their trades?
No. It is a descriptive observation that several members traded the same stock in a short window. It is not evidence of coordination or wrongdoing.
How many members make a herd signal?
Generally three or more members trading the same stock within a tight window, weighted by how concentrated the activity is.