Adaptive Home Field Advantage

This article describes a new method of determining the home field advantage in club football. As opposed to the static method that has been applied so far, from now on home field advantage will adapt to results every day and will be different in every country and for international games.

This article examined the universal phenomenon of declining home field advantage and came up with a method to compensate for this effect. It was however a retrospectively applied manipulation and not future-proof. That is why we will introduce a new adaptive method of determining the home field advantage in Elo points.

The expected number of Elo points to be won by a club in a match should always be 0, regardless if the game is to be played at home or away. That is why the Elo value of the home side is increased by a certain number of Elo points to adjust the probabilities. If in the long run home sides won more points than away sides, then this home field advantage would be too small and would have to increase. Likewise, if in the long run away sides won more points, the home field advantage would have to decrease.

I have discovered that home field advantage can vary a lot depending on the country, so from now on every country will have its own home field advantage number. It is calculated in the following way:
For the first game historically, the home field advantage for a league is set to 100 (250 for international games). For every match, the number of Elo points that the home side won is multiplied by 0.075 and added to this value. 0.075 is not chosen arbitrarily, this is the number where the prediction accuracy is maximised.

This method creates a feedback loop that keeps the home field advantage always close to where it most realistically is. For a list of current and historic values for home field advantage, click here. Rankings will only slightly be affected, as every team plays as often at home as away, odds for single matches however will change.

Created: 23 Mar 2013 - Modified: 24 Mar 2013