Tuesday, December 22, 2009

Effect of Boxing Day Glut of Matches

The English Premier League is unique among top flights in that they play a lot of matches between Christmas and the first few days of the year while most leagues are completely off. Most seasons a team will play on Boxing Day and then again just two days later. Some seasons there will be another match just 2 or 3 days after that so they are playing 3 league matches in 6 or 7 days. This year there are matches every day from the 26th to the 30th of December. Most teams play on the 26th and then on the 28th.

Does this sequence of fixtures help any type of team? It seems like it could go either way. The good teams tend to be deeper in talent so the short amount of rest could help them as they can start fresh players that are still at a high level. On the other hand, fatigue could add some randomness to the short-rest matches. That is probably good for the bad teams since it makes upsets more likely. Perhaps the most sensible guess is that it doesn't really matter; both teams face the same strain.

To test this, I came up with a simple model with just one input for all matches and another for the matches played on short rest during the last week of the year or the first few days of the new year depending on the schedule. The data is all matches since the 1995-1996 season. The input is the difference in average goal differential for the home and away teams in all matches other than the one in question. So instead of the predictive model, I'm actually using data from after a given match took place. For example, if the match is Arsenal at home against Everton two seasons ago I'll take Arsenal's goal differential for the season, subtract off their goal differential in that match, and divide by 37. I then do the same for Everton and the input value is the difference. I then include another variable which takes on 0 for all matches other than those with short rest at the end or beginning of the calendar year. For the matches we are interested in, the value is the same as the other - the difference in average goal differential between the home and away team in all other matches. I then ran those through an ordered logit model to see if there was a difference between the short-rest matches just after boxing day and the regular ones.

In case that didn't make sense, the only thing you need to know is that if the coefficient on the short-rest variable is significant and positive, then that means that the shortened rest favors good teams. If it is significantly negative then that means that the schedule favors bad teams making them more likely to get a result against better sides. If it is very close to zero either way then that indicates that the difference in schedule from the rest of the season doesn't matter either way.

As it turns out, there is no evidence of an effect either way. The coefficient was 0.12 with a standard error of 0.167. The standard error being larger than the value of the coefficient means it is very likely that the difference is just due to randomness. The p-value is 0.472, meaning that there is about a 47% chance of values this extreme if the actual value of the coefficient is 0. That's quite high. There is no evidence of any difference between the post-Christmas group of matches and the rest of the season.

There are reasons to dislike the scheduling, I'm sure players don't like playing so frequently in such a short period of time, but it appears that fairness isn't a factor as it doesn't overly benefit or punish good or bad teams.

No comments:

Post a Comment