Herding
Updated November 10, 2026
Herding is trading toward the visible price instead of an independent estimate. It can tighten a quote without adding information, because the argument that prices aggregate what people know generally assumes those people formed their views separately.
A contract lists at 70¢ on one participant's view. Later arrivals with no strong opinion transact near that level because it is what the screen shows. Volume rises, the spread narrows to a cent, and the quote now looks well supported.
It may not be. Ten trades at 70¢ that each took 70¢ as their starting point carry roughly the information of one. From outside, that market and one where ten participants independently arrived near 70¢ look identical.
- Spread once volume rises
- 1¢
- The quote looks well supported
- Trades at 70¢
- 10
- Each took 70¢ as its starting point
- Independent view behind those ten trades
- ~1
Why independence matters to a price
The case for reading a market price as a good estimate leans on the wisdom of crowds. When many people form estimates separately, their errors point in different directions and partly cancel, so the average lands closer to the truth than most individuals do.
Herding removes the cancelling. If later traders start from the visible price, their errors are no longer spread around the truth. They are clustered around whatever the first participant got wrong. Adding more of them adds volume and narrows the spread without pulling the price toward a better number.
Volume and a narrow spread are among the usual signs of market efficiency, and herding produces both without the independent views they are meant to indicate. A thin or newly listed contract gives it the most room, since a single early trade can set the level the rest of the book anchors on.
Herding vs updating on information
Moving toward the market price is not always herding. If the price reflects information you didn't have, such as a data release or a court ruling you hadn't seen, adjusting your estimate toward it is ordinary updating. The trade then carries your judgment of that information.
Herding is when the price itself is the reason, with no view behind it. Looking at the same 70¢ quote, one trader asks why it sits there and checks whether the reasons hold up. Another buys because it is the number on the screen. From outside, the two trades look the same.
Some forecasters keep the two apart by writing down their own estimate before they look at the quote, then comparing. The gap between the two numbers shows how much of a later view came from the price.
FAQ
What is herding in prediction markets?
Traders taking the visible price as their estimate instead of forming their own. It can make a quote look well supported while the trades behind it carry about as much information as one participant's view.
Is herding the same as momentum?
No. Momentum describes prices continuing to move in the direction they've been moving. Herding is about where traders' estimates come from, and it can hold a price still as easily as push it along.
Does herding make a market price wrong?
Not necessarily. It makes the price carry less independent information than its volume suggests, so the price can still land near the right number, but there is less reason to expect it to.