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TheRoonBa

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Jul 31 07 11:40 PM

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A new ranking system has been in place for a few weeks now. I am currently making small adjustments to the program so the rankings will change slightly over the next few days. I am also re-checking all the results in my archive, so as new matches are added and others deleted, the rankings will also be subject to change.
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#1 [url]

Aug 27 07 2:41 PM

In Principle a ranking system should not be changed too often, or the danger of a bias will become bigger.

But a differentiation of the points according to distance of matches between now and the date a match was played is important!

Because the national team consists of mainly new players every six years. While the elo-system was invented in original for chess-players, which were always the same person.

So (for example) a match, played by Guadeloupe in 1950 against Trinidad and Tobago can not tell us as much about the strength of the Guadeloupe-team today as the last few games, when they won against Honduras and Canada, but lost against Mexico and Costa Rica.

The matches of 1950 till 1990 can only tell us something about the football-resources of Guadeloupe.

Question: am I right, that till 2006 the Roon-Ranking evaluated the match of 1950 and 2007 the same?

Your idea of a number of matches is better than a period of time, as some smaller teams may play too few matches in a fixed period.



But I have some concern about the change (apart from it being a change):
1. It becomes more complicated: till now after a match you could see quite easily, the points one team won, were exactly or almost exactly the points the other team lost. Now the winning team can lose points, because the gained points are less than the devaluation of the tenth last match.
[example: Lithuania played on August 22, 2007 against Turkmenistan. Lithuania won 2:1. Okay that was a relatively poor win for Lithuania (ranked 65th before with 1634 points) at home against a team ranked 130th before with 1422 points. But additionally Lithuania's draw in Italy (2006) was Lithuania's 10th last match and now became the 11th last match - so it drops out of the valuation for the ten-match-ranking.
So Lithuania wins but loses 28 points and 9 ranks. At the same time Turkmenistan looses, but wins 4 points and 4 ranks, because its 10th last match was a "harder" 0:3 loss to Saudi Arabia, now dropping out of half of the ranking]

2. We will have to see how it develops. I could imagine that a series of wins will pitchfork a team too high up.


Conclusion:
A different (higher) valuation of the last ten (or maybe better: 20?) matches ("with more emphasis on the most recent result" (maybe better: results?)) is an improvement.

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TheRoonBa

Posts: 5,508 Site Admin

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Aug 27 07 3:45 PM

The previous ranking was based on the ELO ratings. Therefore, a team gains or loses points in a game, and these points are added to a running total.

The new ranking has 2 parts.

The ELO part is still operational. Therefore, Lithuania would gain points for beating Turkmenistan, and Turkmenistan would lose points.

The new part is based completely on the margin of victory of the game - for example - a 1-0 win against a team with 1500 points may be worth 1600 points, a 2-0 win worth 1700 points (although, I have taken into consideration that the difference between winning 1-0 and winning 11-0 is greater than the difference between winning 11-0 and 21-0).

In this way, a team has a 'portfolio' of its last 10 games in the new section. The last game is multiplied by 10, the second-most-recent game is multiplied by 9, and so on back to the 10th last game, which is multiplied by 1. The total is then divided by (10+9+8+7+6+5+4+3+2+1)=55 to give the team's 'current form' ranking. Teams who have played less than 10 games can still have a ranking based on their first result against a ranked team.

Then, the current form ranking is added to the ELO ranking, and the result is divided by 2.

In this way, neither system has too much influence.

It may be more complicated - but ranking football teams is not a simple problem. Simple solutions will provide simple and basic rankings which do not reflect playing strength or current form. What I am doing is attempting to reflect both playing strength and current form in the same ranking. So, there will be more movement in the ranking but this is what happens in reality. Teams change rapidly, and some ranking systems do not allow this change to be shown quickly enough.

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