How incredible is Leicester’s performance? Efficiency of teams in 2015-2016 Premier League

The performance of Leicester, who has just won the 2015-2016 Premier League title, is with no doubt one of the greatest and most pleasant surprises in European football during recent years. But, how great is this achievement? A way to answer this question is to calculate the efficiency of teams in this league. For that purpose, we consider the efficiency as the inverse of the probability of achieving more points than the actual ones using the odds set by betting houses. The interpretation of this index is quite easy: the closer its value is to 1 the better the performance and the closer to 0 the worse the performance. A further explanation of the methodology can be viewed in this paper of the Journal of Sports Economics.

The table of the efficiency of Premier League teams in the 2015-2016 season is shown below:

Team	Efficiency	Points
Leicester	0.99987	81
West Ham	0.98	62
Stoke	0.81	51
Tottenham	0.80	70
Southampton	0.79	63
West Brom	0.71	43
Watford	0.66	45
Swansea	0.61	47
Sunderland	0.59	39
Manchester United	0.46	64
Arsenal	0.41	71
Liverpool	0.36	60
Newcastle	0.32	37
Bournemouth	0.32	43
Crystal Palace	0.31	42
Everton	0.22	47
Norwich	0.16	34
Manchester City	0.13	66
Chelsea	0.02	50
Aston Villa	0.004	17

Note: the odds are calculated as the average of closing odds in Bwin, Bet365, Interwetten, Ladbrokes and Willliam Hill.

For the Manchester United – Bournemouth game (still to be played) we have assumed a draw.

We can see that the efficiency of Leicester is virtually 1. More specifically, the results show how the probability of having achieved a higher score for Leicester is 1.3/10,000. However, this probability is not completely accurate because the closing odds show, or should show, all the information prior to a given game. So, this probability was incorporating all Leicester’s wins throughout the season. Otherwise, the odds could have been much higher. We could cautiously consider it to be 10 times more complicated, so the probability of Leicester achieving at least 81 points would be around 1/100,000.

The performance of West Ham with an efficiency value of 0.98 is also a highlight in our results. On contrary, the performance of Aston Villa was simply a disaster this season, as well as Chelsea’s, coached by Jose Mourinho for a long period this season.