Monday, March 28, 2011

AFL Power Rankings - What To Do With The Gold Coast Suns?

The AFL Power Rankings are meant to be a reflection of a team's form over their past 22 matches (discounting the pre-season), with more recent matches receiving a higher weighting. However, until next week, the total number of games the Gold Coast Suns will have played is zero. Hence, there is the potential for the Suns to add a great deal of instability into the rankings over their first few matches. This is not only because there will not be a lot of data by which to determine Gold Coast's ranking, but also because there will not be a lot of data to determine a team's relative performance against them. For example, if Carlton beats Gold Coast by 6 goals next week is that a relatively good result or bad result for the Blues?

I like the following solution best. I am going to assume that the Gold Coast, in their first season, are essentially the equivalent of the Brisbane Bears in their first season (1987). In their first season, the Bears had an average net margin over 22 rounds of -25.1 points. I will therefore populate each of the past 22 weeks of data for Gold Coast (thanks to Lauren for this part of the idea) with a net margin of -25.1 points.

The result is that Gold Coast currently sit 16th in the rankings, between Richmond and West Coast. Any team that played Gold Coast next week would have to beat them by 14 points or more (remember there is an adjustment of +12 points for playing in Queensland) for their performance to be considered above par. The best part about this solution is that Gold Coast's ranking will now change at broadly the same pace as other clubs: if they get off to a great start they will move up the rankings, but pretty much no faster than any other team near the bottom who has a few good games. And teams that play the Gold Coast will have their ranking no less affected than if they played any other team down the bottom of the rankings.

It may be that Gold Coast turn out to be a better/worse team than the 1987 Bears, but I think that's a reasonable expectation for them for now.

Until next week...

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