How sure bets affect bookmaker odds

Quotes in the world of betting play a key role in determining the likelihood of various outcomes of events. They are numerical values that indicate the potential winnings of a bet and the degree of risk associated with each outcome. The coefficients can be presented in various formats, depending on the country in which the company is oriented. For example, in decimal format, an odds of 2.0 means that the winnings will be twice the bet. A fractional format such as 3/2 represents the ratio of the winnings to the bet size. The American format, where odds are presented with positive and negative values, indicates the amount of winnings in dollars for a bet of 100 USD.

It is important to be able to interpret odds because they reflect the likelihood of outcomes occurring. The higher the coefficient, the less likely the event is to succeed, and vice versa. For example, an odds of 1.5 means a probability of around 60%, while an odds of 2.0 indicates a probability of more than 50% (due to the bookmaker's margin).

Bookmaker odds are dynamic and may change depending on various factors. These factors include the volume of bets on a particular outcome, news about teams or players, and changes in the assessment of the likelihood of event outcomes. And this same volume largely ensures the emergence of arbitrage situations, such as surebets.

  • The first reason for the formation of bookmaker sure bets is related to differences in methods for assessing the probability of event outcomes between different bookmakers. Each bookmaker has its own analytical tools and models, on the basis of which they determine quotes for certain outcomes. This may result in one bookmaker estimating the probability of success of one outcome higher than another and therefore offering a lower odds.
  • The second factor is the reaction to user actions. When the majority of bets are on one outcome, bookmakers will change the odds to balance their line. As a result, the odds for other outcomes may change in such a way that it becomes possible for bookmaker arbs to appear.
  • The third factor that can lead to the appearance of bookmaker sure bets is time delays in updating odds by various bookmakers. Due to different systems and technologies for updating betting and odds information, some sportsbooks may update their data faster than others, which can also create an opportunity for arbitrage. Well, don’t forget about the margin, the size of which directly affects the quote and, accordingly, its discrepancy with the odds for the same event in other bookmakers.

Thus, we can conclude that users who bet on sports through bookmaker arbitrage can have a direct influence on the writing of odds. The difference of which is detected by the scanner. And the more popular and in demand any sure bet becomes, the more the initial odds can change. (This may also lead to other reactions, but more on that later).

Data analysis of arb

To clearly understand what we are talking about, let’s look at several examples of third-party influence on bookmaker quotes. As noted earlier, odds are unstable and can change at literally any touch, which means it is not surprising that even a relatively small bet can be decisive. For example, a large number of bets are made on any outcome of a football match, even without an obvious favorite. In this case, one of the arms of the line begins to greatly outweigh, which does not go unnoticed by the bookmakers. Professional arbers have the concepts of Initiators and Donors, which we have already talked about earlier on our website. Bookmakers are starting to equalize the quotes, but even this does not always help, because there may be too many bets on one event.
As an example, here is the current table, which includes several recent matches:


First team winning odds

Odds for a draw

Second team winning odds

Total bet amount in euros

Amount of bets per option in euros


Odds change after two days

Rio Ave – Sporting CP (Liga Portugal)




1 991

1 991 for Sporting victory



Almeria – Atl. Madrid (LaLiga)




6 064

6 056 for Madrid victory



Melbourne Victory – Central Coast Mariners  (Australia A-League)




7 736

7 711 for Melbourne victory



Instituto – Godoy Cruz (Argentina Copa de la Liga Profesional)




11 340

11 306 for Instituto victory



Sunderland- Swansea (Championship)




2 730

2 711 for Sunderland victory




The basis is taken from data from the Betfair exchange, which, in this case, much better reflects the real outcome of the layouts and preferences of betters. There are several key points:

The distribution of amounts is extremely uneven. It is worth noting that, for example, in the Argentine championship match, the odds for the home team to win are more than 2, but 99.7% of bets on the outcome are made on them. By simple calculations, it can be determined that while 11,306 euros are bet on Instituto's victory, their opponents' win and draw are worth only 34 euros in total.
It is important to understand that bet amounts do not reflect the number of bettors who placed the relevant bets. In other words, one exchange user could have bet the conditional 6 thousand euros on Atlético’s victory, or several hundred could have.
In this case, what is surprising is the fact that the quotes for almost all outcomes managed to grow a little. In a standard bookmaker, the situation would have developed differently, but here the main difference between the exchange and the company is clearly visible - the exchange itself cares little about quotes, because earnings come not from the “correct” odds, but from users. This allows even loads in bets to remain at the same level, giving other clients of the site access to exactly the same odds.
The volume of bets on the exchange is noticeably smaller than in bookmaker companies. Therefore, there are practically no situations where 100% of bets are placed on one outcome, as in the case of the Sporting match. However, on small markets the overweights can be quite significant, which is why bookmakers have to significantly change the initial quotes.
Separately, it is worth noting an interesting fact: out of the five matches presented, not a single one ended with the result that received an overwhelming advantage in the amount of bets. Atlético and Sporting ended their games in a draw, while Melbourne, Instituto and Sunderland lost. However, the influence of arbs should also be considered. Here, for the purity of the experiment, we will consider several options that differ in time periods. Let’s take a popular and popular scanner – Surebet. We will choose an arbitrage situation with a yield of up to 1% inclusive. As a bookmaker, let’s consider Pinnacle, which is loyal to arbers.

The found arbitrage situation with a small profitability shows that Pinnacle has a rather favorable odds for the Conference League match between the Dutch Ajax and the English Aston Villa. A handicap of +0.5 on the hosts is offered at odds of 2.3, thanks to which a surebet has arisen with several bookmakers at once. And indeed, this is exactly what happens:

Here it is also worth paying attention to the opposite outcome - the victory of Aston Villa is offered for 1.641 (noticeably lower than in the Mozzart bookmaker, which is presented on the second shoulder). The gap between the two quotes was 0.659 points. Quite compact line formation. This arb appeared two weeks before the start of the match. For most arbitrageurs, this is too long a time, since if this situation is identified immediately, then all the allocated funds will hang like a dead weight until the final whistle in the Netherlands.

Accordingly, it is not surprising that a few days later, even though the surebet continued to be in the scanner line, the odds for the presented outcomes did not change even by a thousandth. Most of the audience simply did not use it due to a time gap, so the size of the odds was not seriously affected. The bookmaker, quite logically, did not take any action to correct the situation, since nothing had to be corrected. The movement will begin only a couple of days before the start of the match, or even a few hours before the starting whistle.

Another example on the same conditions considers an sure bet that appeared 4 days before the start of the match:

Colombian football championship match - Fortaleza vs Alianza. For the guests' handicap of +0.5, Pinnacle gave 2.04, which gave rise to an arbitration situation.

The second leverage was again offered in companies that were far from the most popular and in demand, but we don’t need to indicate them, and this arrangement is suitable for example. If in the previous example there was a compact line formation, then what is it like here? The hosts were given 1.826 to win – the difference between the quotes was only 0.214.

Three days later, the day before the meeting, the situation changed:

This example perfectly reflects the process of work of a competent and experienced, truly large bookmakes during the load on one of the shoulders of the outcome. They do not try to trivially reduce the quote to a minimum, scaring off other applicants, but operate with all available data for equalization. That same 0.5 away handicap increased in numbers, and the coefficient on it was already 2.12 - an increase of 0.08 points. It is also worth noting the movements in other quotes, which also do not stand still. A home win is now offered for 1,787 - the numbers have dropped, meaning the gap between the shoulders has widened. The situation most strongly affected the victory of the guests - this option increased by almost 0.3 points. At the same time, in the Rivalo, presented on the second side of the arb, the odds for the home team’s victory over the past days have decreased by almost 0.2 points. This is an example of actions for a simpler bookmaker - reducing a suspicious quote in order to minimize possible risks.

The third example considers a surebet one day before the start of the match:

Scottish League 1 match between Stirling Albion and Hamilton Academical. First of all, if such an opportunity arises, it is worth noting an error in the scanner: as you can see in the screenshot, Pinnacle offers a +1 handicap for the home team on corners. However, it is not. Firstly, the second leg does not have any notes about corners, and secondly, in fact, Pinnacle did not provide the opportunity to bet on such an outcome at all. As you can see, quotes for corner handicaps start at +2:

Even if we assume that such an offer actually existed, but disappeared, from other odds one can understand that for a handicap of 1 on corners +1 they would have given noticeably more than 2.02. But for handicap 1 on goals +1 they actually gave exactly the coefficient that was in the surebet:

A few hours passed after the arbitration situation appeared, and the situation in the line changed:

This time, the loaded quote has already dropped by 0.059 points, and the reverse leverage, on the contrary, has grown. This is a standard quick reaction when the coefficient is pressed down under the load of bets, and its reverse side, like on a classic scale, rises up. But here there is no doubt that the bookmaker will not stop with these changes and will continue to adjust the line until the situation stabilizes on all sides. This will continue until the starting whistle and even after it.

Thus, we can note two methods of action on the part of bookmakers in the event of arbitrage situations with their participation: some reduce the loaded outcome, making it less attractive to users, and others correlate all the quotes surrounding the outcome in order to achieve balance. If there is too much time before the surebet, then the actions of users will only be observed without taking active actions.

We can say that the appearance of a surebet has several effects on the market, including:

  • Increase in the volume of bets. The surebet attracts more users who are eager to use this opportunity for a guaranteed win. This can lead to a significant increase in the total volume of bets on a particular event.
  • Change of odds. When bookmakers detect arbs, they can react quickly and adjust their odds to minimize losses. This may lead to changes in odds not only in the bookmaker who discovered the arb, but also in other bookmakers, to maintain the level of competitiveness.
  • Increased risk for bookmakers. Arbs create additional financial risks for bookmakers, especially if they cannot be quickly noticed to correct the situation.

These effects demonstrate that sure bets have a significant impact on the betting market, affecting both bettors and bookmakers.

Conclusion about the influence of arbs on odds

Speaking about how sports betting through bookmaker arbitrage can influence odds, we looked at clear examples showing that quotes can change quite significantly after sure bets appear. However, despite the existence of patterns, each bookmaker acts in such a situation at its own discretion. Someone reacts only when bets on any outcome have already approached a critical value, and someone monitors surebets scanners in order to quickly respond to situations in which their own company appears.

To summarize, we can say that the influence of bookmaker sure bets on odds is obvious. No bookmaker's margin can cover the losses that the BM will incur in the event of an error in the line that was not detected in time. That is why not only analysts are always on guard, but also special programs that carry out adjustments and respond to external factors.