Pythagorean 2.0 Projections: 2008-09 English Premier League

A few days ago I presented Pythagorean projections for this year's English Premiership, based on the formula that I developed.  I didn't like the fact that the projection overestimated league points, but felt that perhaps the estimated league position might be useful.

Over the weekend, I took a much closer look at the derivation of the Pythagorean formula and made some necessary corrections to it.  I am very pleased to say that the new version is a huge improvement on the original.  I am not pleased to say that the resulting formula is extremely complicated and not as simple as the baseball Pythagorean, but that is the price to be paid for three possible outcomes to a match.  I'll give more details in a separate post.

After the jump I present the mid-season tables for this year's Premier League with Pythagorean estimated points.  I used a league Pythagorean exponent of 1.70.

Club
GP   GF
 GA
Actual Pts
Predicted Pts
+/- Point Diff
Chelsea 20 45 16 45 44 +1
Manchester United 20 45 18 43 43 0
Arsenal 19 51 21 41 41 0
Tottenham
20 42 22 37 39 -2
Manchester City
19 38 27 35 32 +3
Aston Villa
20 29 18 35 35 0
Liverpool
20 37 25 33 35 -2
Birmingham City
20 20 18 32 28 +4
Fulham
19 24 19 27 29 -2
Sunderland
20 28 31 23 26 -3
Everton
19 26 32 22 23 -1
Stoke City
19 15 23 21 18 +3
Blackburn Rovers
20 20 35 21 19 +2
Burnley
20 22 40 20 17 +3
Wolves
20 17 36 19 14 +5
Wigan Athletic
19 21 44 19 16 +3
West Ham United
20 28 37 18 23 -5
Bolton Wanderers
18 26 36 18 15 +3
Hull City
20 20 42 18 20 -2
Portsmouth
20 18 32 14 18 -4

As you can see, the point spread between the Soccer Pythagorean and reality is down to a mere +/- 5 points.  A difference of one to two wins, or a win and a draw or two, essentially.  This is a much better metric, and as commenters have said, it's more useful to say something about points than league placement.  

The teams with the large point spreads attract the most attention — on New Year's Day, Birmingham City and Wolverhampton Wanderers have outperformed relative to their statistical expectations, while West Ham and Portsmouth have underperformed significantly.

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