Bookmakers’ line

Dmitry Khlestkin


Forming the line

The line is formed by analysts of a bookmaker that evaluate the probability of various events in the match, using math and sports statistics. It is noteworthy that the human factor plays a small role in forming the line nowadays. Most of the work is done by robots.

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Large bookmakers make up their own line, while small companies use the providers of betting products, such as Betradar.

Adjusting the line

Bookmakers adjust the line, relying on pre-match events (such as key players getting injured) and events during the match in case of live-betting. This is called line adjustment.

Also, a bookmaker adjusts the line when a lot of punters bet on one particular outcome of an event; he cuts the odds for the outcome which makes the other possible outcomes of the game more attractive. This is called line overload.


Betting markets are separate kinds of bets in a bookmaker’s line, consisting of a list of possible outcomes with odds. For example, “1 × 2”, “Both teams to score – yes/no”, “Total goals over/under”, “Win in the first half and match”.

Types of lines

There are two approaches to forming the line. The first is a fundamental approach where a bookmaker estimates the probability of an event and provides the odds with the margin. The second approach is a market one, when a bookmaker takes into account the estimated betting load on a particular outcome and corrects the odds considering these expectations. Bookmakers with different business models have different approaches to the creation of the line. Many companies use different approaches for different groups of markets and events. In general, market-based approach is more often used by low-margin bookmakers.

Action line

A wide bookmaking line is the one that provides a big variety of events with numerous additional markets (action line). Popular events, such as the Champions League final, may have up to 800 markets. The more exotic is the market, the higher is the margin, as bookmakers are often mistaken in assessing the probabilities of the outcomes in matches of which they have little information.

Line strength

A strong line, according to professional punters, is the one that is strong enough to stand arbitrage situations (surebets). When shoulders of  surebets often wins, it makes the line weak. As a rule, a strong line is a dynamic line that quickly responds to market fluctuations and provokes arbitrage situations. Pinnaclesports, Betfair and Sbobet are among the bookmakers to have it.

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