How the odds are formed in the bookmaker's line.
What are coefficients and how are they formed
Each coefficient reflects the probability of the corresponding event according to the bookmaker. Ideally, the sum of the probabilities of the outcomes of an individual event should be equal to 100% (or just one). Totals, the winner of a match in tennis is a two – way event, the winner in football is a three-way event (win 1, draw, win 2).
Coefficient – the inverse of probability.
K = 1/P, where K is the coefficient, P is the probability in the range from 0 to 1.
For example, if the chances of winning two tennis players are estimated equally (50% or 0.5), then theoretically the coefficients for their victory should be equal:
K1 = K2 = 1/0, 5 = 2
It is impossible to see such a picture in a real bookmaker's line, because it adds its own Commission to each probability. In betting, it is called margin.
Margin
Margin is one of the protection mechanisms that a bookmaker uses to keep the total of all bets in profit. This is a certain percentage that is added to the probability of each possible outcome.
Why are the coefficients in the line constantly changing
The influence of bookmakers on odds is not limited to calculating probability and adding margin. Otherwise all the values would remain unchanged from the moment of getting in line and before the start of the event. In fact, they change all the time.
The players themselves are primarily responsible for this. Of course, there are factors that do not depend on them. Such as an unexpected injury, firing of coaches and even the changing weather conditions. All this can theoretically affect the result, and therefore affects the probability of each outcome, from which the coefficient is calculated.
But the main contribution is still made by the activity of players. When the total amount of bets on a particular outcome begins to increase dramatically, the bookmaker lowers the coefficient. Accordingly, the opposite value / values increases.
This mechanism allows the bookmaker to protect itself from unnecessary expenses, reducing the total amount of payments in case of winning the favorite. However, it also works differently for different markets. For top Championships, only a large amount of bets shifts a number of related coefficients, while for unpopular events, even one large bet can significantly change the line.