Sunday, 20 July 2014

Books And Ratings Compared EPL 2014-15

I have spent most of this weekend building a new spreadsheet (although model sounds better) for the lower leagues in England. It may well prove to be too much work to maintain this, but others have success in the lower leagues, and I thought I would give it a try. The initial ratings are based on those on the website, but mine will soon diverge and take their own shape as the results start coming in.

The close season is always disruptive to ratings but after a handful of games they correct themselves. Unless your club rating is based on individual player ratings, there is no objective way of incorporating dramatic changes at clubs. In the EPL, the activity at some of the top clubs this summer has impacted last season's closing ratings.

Liverpool finished 2013-14 in second place, not only in the EPL, but also in the Cassini Ratings, and were joint second in Statto's ratings too. Currently, based on Pinnacle Sports and Betfair's prices, they are rated fifth, behind favourites Chelsea and followed by Manchester City, Manchester United and Arsenal, and my current rating of second is likely to soon be adjusted down.

Southampton are another club where significant changes have taken place. Currently rated 7th by Cassin and 8th by Statto, they are ranked 11th on Betfair.

Assessing new (promoted) teams is also problematic. For their initial Cassini ratings, I use the performance of promoted teams over the last ten seasons as a guide. The last 30 teams promoted to the EPL have averaged a finishing place the following season of 15.2, and in 9 of the last 10 seasons, at least one promoted side has been relegated.

One odd fact is that the promoted Champions actually fare worse on average than the runners-up and play-off winners. Five Champions have been immediately relegated, including the last two of Reading and Cardiff City, while only two runners-up have suffered the same fate, and none since 2007. Five play-off winners have also dropped immediately, but the last three all finished highest of the promoted teams in the following season.

So it's a little surprising that the sportsbooks have the three promoted teams to fill all three relegation places. Here are the predicted finishing positions based on the bookies, along with the Statto and Cassini ratings.

Statto's rating of Leicester City in 10th place seems a little high to me, and both our ratings for Newcastle United are probably a little low. They certainly ended the season in poor form, but then they had nothing to realistically play for over the last few games. I seem to be a little high on West Bromwich Albion where the expectation seems to be of just about avoiding relegation.


fairfranco said...

out of interest do you know if Statto's ratings have been of any use over time?

Would be good to see historical results with ratings at the time alongside them to get a grasp on some accuracy.

Matthew Trenhaile said...

I would also be interested Padrino if you had any experience regarding the validity of the Statto ratings. Once upon a time I used to paper trade a range of ratings system while betting my own but it became too time consuming. If I remember correctly I found the Statto ratings were very weighted to long term quality over short term form and I never could devise a method for incorporating their trend rating in to a betting system. They seem very similar in style to the Racing Football Outlook newspaper football ratings and both seem to have their origin in Elo. They seemed lackluster in the divisions where more complex models were rife e.g. EPL and better in the lower class European leagues. For top leagues a good free option remains Dectech for Poisson style goals for and against ratings.


Matthew Trenhaile.