Three reasons a price moves, and how to tell them apart
A price that shortens is often read as a signal that somebody knows something. Sometimes it is. More often it is one of two duller explanations: a lot of ordinary money has arrived on one side and the book is balancing its liability, or a competitor moved first and everyone else followed to avoid being picked off. Distinguishing between these is worth more than any tip, because only one of the three tells you anything about the event itself, and the other two tell you about the market's plumbing.
Information, money and liability
Information moves prices when something changes in the world: a team sheet, an injury, weather at a racecourse, a suspension. Money moves prices when volume piles onto one outcome and the book adjusts to reduce what it stands to lose. Liability moves prices when the book's existing position, accumulated over days, becomes uncomfortable regardless of what has arrived today. The three often happen at once, which is why reading a single movement in isolation is unreliable.
Information-driven moves
These tend to be fast, one-directional and mirrored everywhere within minutes, because every firm sees the same news. If a price has moved sharply at every operator you can check, information is the likeliest explanation. It also means the new price already contains the news, so the opportunity has passed.
Money-driven moves
Volume on one side pushes a price out on the other as the book protects itself. These moves are often uneven between operators, because each firm carries a different book. A price that has drifted at one firm while holding elsewhere usually reflects that firm's own exposure rather than anything about the event.
Liability management
A book with a large accumulated position may move a price to attract money on the other side, even without new information or a rush of bets. This is why a price can drift on a quiet afternoon. It is bookkeeping made visible, and it is the least informative kind of movement for a bettor.
Early prices and closing prices
The price at market close is generally the most accurate one available, since it has absorbed the most information. Early prices are less accurate but carry a larger margin. Neither is a promise about anything: an accurate market is still a market that is wrong regularly.
Questions readers send us
Should I follow a shortening price?
Following a move means accepting a worse price than the people who moved it, which is a poor structural position. Whether it is sensible depends on why the price moved, and that reason is usually invisible from the outside. It is not a strategy that guarantees anything.
Why do two operators show different prices?
Because they hold different positions, take different customers and have different appetites for risk on that event. Divergence is ordinary. It is also the reason comparing prices is worth doing before placing a bet rather than after.
