What are Expected Points (xP) and how to use them in football betting
It was recently announced that FIFA 22 will include modern footballing statistics such as Expected Goals (xG). The way we analyse football is continuing to involve and a further enhancement of Expected Goals is Expected Points, or for short xP. We’re here to run you through the basics on what exactly expected points are and how it can be related to football betting.
xG Basics
In order to work out Expected Point totals, Expected Goals data is needed, so let’s refresh ourselves on the basics of xG. Essentially, Expected Goals takes out luck and randomness from football. It tells us who are actually the best players and teams and who are just lucky. The main purpose of xG is to measure performance rather than results, so instead of seeing how many goals a player or team actually scored, we can see how many they should have scored, based on how well they performed.
The Expected Goals method works on the basis that not all shots are of equal value and incorporates shot quantity and also shot quality. Each shot is given a probability of being scored and is then converted into the shot's value.
For example if Manchester City play a match against Liverpool and Pep’s side have five shots from long distance, those shots are each worth 0.1xG. At the end of the match, their total shots values can be added together to reveal their team xG total for the match, which in this case would be 0.5, so City would have been expected to score 0.5 goals in this game.
Analysts and punters can use xG to then work out each team's Expected Points total from a game.
What are Expected Points?
Expected Points indicates how many points a team could have Expected to have taken from a game, based on the scoring opportunities that they both created and conceded in that game. The more on top one side is, the more xP they will take from the match.
The maximum number of Expected Points a side can take from a match is three and if a team were to take every shot in a match without conceding a single shot, they would amass 3xP.
On the flip side a team who concedes every shot in a match, without conceding any, will amass close to 0xP.
However, it is incredibly rare that one team would collect the entire 3xP from a match. Dominant teams normally receive between 2.1xP and 2.8xP, while teams who are dominated will collect around 0.1xP to 0.5xP.
One thing worth noting here is that the points totals of the two teams do not have to add up to three, with one point for a draw changing this.
How are Expected Points calculated?
Companies such as Infogol and Understat produce their own Expected Points data and the basics behind how they are calculated can be simplified into three steps.
- Collect the values of each shot’s xG that have been taken and conceded during the game.
- The match is then simulated several thousand times in order to find the probability of each team winning, drawing, or losing the match given the shots they have taken and conceded. Expected Points simulators can now be found online free.
- The probabilities can then be used in an Expected Value equation to work out how many points a team could have expected to have earnt.
Just like with Expected Goals, Expected Points show us how many points a team deserved to pick up, regardless of the result of the match.
Expected Points data can be added up to show the ‘actual’ performance levels of teams over the duration of a season, allowing analysts to measure performance rather than the actual result.
Relating xP to football betting
By adding together the Expected Point totals that a team has collected throughout the year, we end up with what is sometimes referred to as a ‘Justice Table’. Below we can see a table containing data from Understat. This shows the actual position and points in the Premier League in the 2020/2021 season, along with the Expected Points (xP) totals for each team and where their resulting position in the Justice Table.
A nice example of how you can potentially convert this knowledge into your betting would be to look at Brighton. Adding up all of Brighton’s 38 xP totals from their games last season gives a total of 61.4(xP). This is the number of points which the Seagulls deserved to pick up when you take luck out of the league table.
In reality, Brighton collected 41 points and finished 16th in the table in 2020/2021. This is a much lower total number of points than what you would expect given their performances. Graham Potter’s side collected 20.4 points less than what they deserved based on xP.
It would be safe to say that Brighton were in fact unlucky to finish as low as they did in 16th, with the Justice Table above ranking them all the way up in 5th. This may leave analysts and punters inclined to believe that Brighton will finish much higher than 16th this coming season based on their Expected Points total from the most recent campaign.
However, it’s worth noting that bookmakers do take note of data such as this and their odds on offer reflect this. Variation in price can be found and a good example would be, again Brighton, who are priced up at just 11/1 with Paddy Power to finish inside the top-four this season.
That’s a massive overreaction to Brighton’s strong xG and xP data from last term in our opinion. The 11/1 on show from Paddy’s is shorter than Aston Villa at 14/1 and is the same price as Everton and Leeds for context.
As mentioned, though, variation in price can be found in these markets at this time of year and William Hill are actually 40/1 on the same selection of Brighton to finish in the top-four. You can compare the full market below.
