The odds on a match do not stand still. A bookmaker posts them several days before the game, then adjusts them dozens of times, and by kick-off the price can differ from the original by 10–20%. The two extreme states of this line have their own names and their own meaning.
The opening line
The opening line is the first price a bookmaker posts on a market. It is built from the bookmaker’s model and from how competitors opened, and so it contains the most errors: no line-ups yet, no reaction from bettors, low stake limits. It is at the opening that those who estimate probabilities themselves most often find value.
The closing line
The closing line is the price at the moment the match starts. By then the line contains everything the market has managed to learn: announced line-ups, injuries, weather, and the money of professional bettors, which bookmakers follow more closely than their own model. The closing prices of low-margin bookmakers are the most accurate publicly available estimate of an outcome’s probability, which is why picks are compared to them when computing CLV.
What happens in between
Line movement is the sum of two forces. The first is information: a line-up comes out without the main striker, and the price on the home side rises. The second is money: large bets on one outcome make the bookmaker cut the odds to balance the risk, even without any news. You cannot tell one from the other by a single price, but you can by the pattern: a sharp shift minutes before kick-off is usually about line-ups, a slow drift through the day is usually about money.
A special case is the “steamer”, or dropping odds: a price falls noticeably faster than neighbouring outcomes, and at several bookmakers at once. It is the trace of the market as a whole re-pricing the event. The day’s steamers are collected on the dropping odds page.
What the service shows
- On the match page: the opening price and the current price for every bookmaker and every market, with the difference between them.
- On head-to-head and match pages: the movement of the main market from the opening through snapshots at 75, 60, 30 and 15 minutes before kick-off.
- On a pick’s page in the verifier: three points, the opening, the price at publication and the closing. CLV is computed from them.
Odds are collected from 14 bookmakers; the verifier’s reference line is Pinnacle’s: it has the lowest margin and the highest limits, so it is closest to the “true” probability. Where the data comes from and how often it updates is described in the article on data sources.
How to use this
It makes sense to compare your pick not with the opening and not with the current price, but with what the price will be at kick-off. If you regularly take an outcome that later “steams” in your direction, you are ahead of the market. If the line moves the other way after your publication, the market disagrees with you, and the statistics are on its side. How accurate the closing line really is, in real numbers, is shown in the study on favourites and the closing line.