The Betfair Prof / Leighton Vaughan Williams / 24 November 2009 /

Did you know that England are the third best team in the world? Yes, I'm talking football. At least that's the finding of the sophisticated forecasting methodology employed by ESPN in their SPI (Soccer Power Index) ratings.

So how are the ratings calculated? Basically, there are four steps. The first is a calculation of a 'competititiveness coefficient', which assesses how seriously each game in the database is being treated by the teams involved. For example, a World Cup qualifier will be treated more seriously than a 'friendly'.

The next step is to derive match-based ratings for all international and club teams. To do this, individual games are evaluated based on the number of goals a team scores and concedes relative to the quality of the competition, adjusting for home advantage.

The third step is to derive player-based ratings. This is an assessment of the quality of the particular players in an international team's line-up based on their performance in both club and international play. The fundamental requirement here is that the sum of the ratings for all individual players in a team must equal the team's ratings for the game.

In the model, the scorer of a goal is allocated half the credit for the goal, with the remaining half of the credit being distributed between the other players who are on the pitch when the goal is scored. Defenders are allocated a smaller share of the credit than forwards and midfielders. The converse applies to goals conceded.

The model also includes player debits for own-goals and for receiving red and yellow cards. All the ratings described above include a recency weighting, so that a game played 6 months ago, for example, receives a greater weighting than a game played 2 years ago. The final step is to combine the team and player data into a composite rating, based on the team that is likely to be actually used in a particular game.

As such, the methodology is predictive rather than backward-looking, and can be used to forecast for example which team is at an advantage in any individual World Cup 2010 encounter. The SPI ratings can range from a theoretical minimum of 0 to a theoretical maximum of 100.

There is an additional footnote - that teams playing very strong opponents are likely to perform a little better than their overall rating if their defence is their relatively strong suit, whereas the converse applies when playing weaker teams.

All we need now is to input the data. Fortunately, the work's been done for us and here are the top ten teams at the time of writing with their current respective ratings and FIFA ranking in brackets: Brazil (88.7, 2), Spain (87.5, 1), England (86.0, 9), Netherlands (83.8, 3), Argentina (83.6, 8), Germany (82.3, 6), Portugal (81.2, 5), Chile (81.0, 17), Ivory Coast (80.7, 16), Uruguay (80.4, 19).

At the time of writing, the Betfair prices closely reflect the SPI ratings, the only significant disparity being Uruguay (ranked 10th on SPI, but just joint 18th by Betfair traders, who are in closer agreement with FIFA's ranking of 19th). So just how good are the Uruguayans? It'll be interesting to find out!

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