## SHORT TERM BETFAIR FOOTBALL TRADING MODELLING

### 1. General

A well known trading pick in Betfair Exchange market is the back/lay arbitrage in Under 2.5 market at the first 10-15min of a football game. When the game starts and as there is no goal, the odd of Under 2.5 market is reducing as it is shown in figure 1. This is the case of placing a back bet before the game and a lay bet when 10÷15min of the game have been played.

We then have to answer the following questions:

What is the probability of scoring a goal during the first 10min of a game?

Which are the best time intervals during a football game for a short term trading?

Next Goal online software offers the modules to perform such calculations using previous historical goal data. The user has the opportunity to select time intervals of a game, in order to have probabilities for the score status.

Figure 1: Betfair diagram of Odd fluctuation during a game

It is assumed, that the reader is familiar with software components and procedures. It is very important to mention that probabilities are based only in historical goal data, without any reference in other game factors, such as players, red cards, etc., that may also affect the result of the game. Therefore, it is suggested that one uses the results only as reference values that need further readjustment according to other factors, as mentioned above.

### 2. Trading Modeling

A trade modelling example is presented below for teams PAOK and ARIS from Greek Superleague. The scope of the analysis will be to find the probability for the score (0-0) to remain or to change inside time intervals of 2min during the first half time of the game.

The results of such a calculation are shown in table 1. Data sampling of goals was selected as «Home-Away» from season 2008 up to 2011. That means, the analysis includes all matches played by PAOK as «Ηome» and respectively by ARIS as «Away». Taking into account the results, the best Trading has to be done between 4-6min, 16-18min and 25-27min. These time intervals during the game show the less probability (below 4%) of the existing score (0-0) to change. On the other hand, time intervals between 22-24min and 34-36min show high change-of-score probability (above 10%).

Table 1 : Trading Probabilities between Time Intervals by Next Goal, Data Sampling Home-Away

Table 2 shows the same calculations assuming different data sampling of goals “Home & Away-Home & Away” that means the analysis includes all matches as «home & away» from PAOK and ARIS. Time intervals between 4-6min & 25-27min show the less probability (below 4%) for the existing score (0-0) to change.

Table 2 : Trading Probabilities between Time Intervals by Next Goal, Data Sampling Home & Away for Team (1) and Home & Away for Team (2)

As indicated through the results' analysis, a safe back to lay trading must be placed between 4-6min & 25-27min of the game. Then rises the question of the betting strategies that have to be followed, if there is a goal during these trading periods (4-6min & 25-27min). Next Goal software offers the tools to model such a case.

The possibility of having the first goal during the 2min-4min is from 2.41% up to 3.05%. On the exact time that the first goal is scored, the odds of Under 2.5 increased abruptly. After a period of time during the game (usually 20-30min), that no other goal is scored, the odds of Under 2.5 market reduces to a price similar to the price offered before the first goal.

A complete trading modeling has to assure that a goal is scored during the trading period. So, when a goal is scored during trading time interval (4-6min), trading has to continue for at least 20min more, that is until the 26th min of the game. The possibility of having another goal (more than one) between 6min to 26min is estimated at 36.36%, as it is shown in figure 2 and figure 3. Figure 4 shows the same trading modelling for making a trading from 25min to 27min and then until 47 to reduce your money loss in case of a goal is scored during 25min to 27min.

Figure 3: Next Goal Predictor menu assuming Scenario of 1goal until 6min and search probability until 26min.

Figure 4: Diagram of Betfair Trading Modeling by Next Goal, Time Interval 4min to 6min.

Figure 5: Diagram of Betfair Trading Modeling by Next Goal, Time Interval 25min to 27min.