Sunday, August 24, 2014

AFL Power Rankings: Round 22 2014


Port Adelaide’s return to form on the weekend, in which it did more damage to Carlton than Neil’s bowels did to Will’s face in the new Inbetweeners flick, sees it re-enter the top four in the rankings. Port’s win also shores up the decidedly non-Victorian feel that the top of the rankings have had in 2014, particularly in the second half of the season. Indeed, the last time the non-Victorian teams were this dominant Twitter had just been launched, and the Australians were winning World Cup matches.


Carlton is the obvious team to spotlight here after it undid much of its progress in recent weeks by getting Neiled on by Port. Things have not really gone right for the Blues since they spent over $600,000 a year on a midfielder that averages 17 disposals a game. As shown in the major American sports league being able to pay big money to lure players away also means that teams need to be judicious in which players they give that money to. (To be fair to Dale Thomas though, he is far from the only reason for Carlton’s mediocre form this season.)


Adelaide moves above North Melbourne despite losing to the Kangaroos on the weekend. The Crows only lost narrowly, and even though the match was played in Tasmania I have counted it as a home match for the Roos, with the usual +12 points home ground advantage. This is consistent with how I treat Hawthorn’s Tasmanian matches against non-Victorian sides. Should the same logic apply to North Melbourne though? What do readers think?

Also of note: next week, for the penultimate rankings of 2014, I will do my usual summary of the season.


Manikato888 said...

Gday Troy

It's a "string" issue, as in "how long is a piece of string?"

More specifically, it depends I think on HOW you calculate Home Ground Advantage HGA).

To explain further, AFL is unusual in that you can have this situation you flagged with a Victorian team being at home, but in Tassie. PUt differently, here is a team who technically has the HGA but is not playing at home that week, The game is at a more a neutral ground. And, sometimes (like in the Nth Melb case) this is actually played interstate.

There is a lot of research on HGA,both for AFL and other sports. These studies typically examine various factors such as: travel time, ground "familiarity" (e.g. the number of times a team and players have played at that ground), effect of the crowd, and even secondary effects such as the "pressure" the crowd puts on the umpire, and the "bias" it creates in favour of the home team.

The latter shows that home teams get more free kicks overall, so that theory may well have some merit.

What is interesting to me though is in all cases I have read:

a) the effect is measured, but
b) no-one I have read is able to prove definitively WHY.

It just is.

The research generally concludes to this effect:

"Team A playing at XYZ against B have a 4.23 point advantage on average, but really, that's as far as we got."

And that's the "string". Put differently, it depends on how strongly you agree or disagree with the various factors i.e. what you see as important for HGA.

Overall, having looked at it myself in some detail (way too much detail, my long-suffering partner is too polite to say, or yell), what is widely accepted from the research?

Travel time is VERY important.

Put simply: the further a team has to travel to play, the greater their disadvantage. And the flipside? The home team has a corresponding advantage.

I see this in AFL especially for the WA-based teams (and to a slightly lesser degree, the SA-based teams).

If people want to explore HGA further in an AFL context they may like to look at the following paper:

Chapter 4 Home Advantage, in Ryall, R. and Bedford, A. (2011). Independent effects that augment home ground advantage. Journal of Sports Sciences.

It also has extensive references, so readers can quickly find what other research shows.


Roby said...

You'll see that North in BA matches have shown no increase in performance over Etihad or MCG or a high differential in win/loss, unlike Hawthorn at AU.

Manikato888 said...

Sorry, I don't see any of that, mainly due to small #s.Maybe I missed something.

The below link shows Nth only ever playing six games at both BA and AU (the old York Oval) respectively. But doing OK comparatively. 6 and 6...not that twelve games count for much.

Hawthorn have played many more times in Tassie, but again this is a very, very small sample.

Troy Wheatley said...

Hey, thanks for the input.

In picking HGA I used fairly rough estimates. Essentially it is +12 in most cases, except I reduced it to +6 for Sydney v Victorian teams. That seemed to match up reasonably well with the data at the time, but I didn't spend more than an hour or two looking into it. Apart from the different adjustment for Sydney-Victorian teams that doesn't take into account travel time, which it sounds like it probably should.

I then started adjusting for Hawthorn's games in Tassie because it looked like their performances there were similar to those in Victoria. I also reasoned that non-Victorian had to travel further to get to Tassie than Hawthorn did, and that was probably an advantage to the Hawks.

The travel time argument could also work for North, although as noted above it does not mean much if not backed up by actual results. Although as noted above also there is only a very small sample from which to draw conclusions.

Next year I might have a quick look back over North's matches there and try come up with a more informed adjustment (if any applies).

Thanks again for your thoughts.

Manikato888 said...

No worries Troy, glad it was useful.

Your logic's pretty sound based on what you are saying here.

If you want to email me directly I can send you my tables. I have looked into it in a fair bit of detail and would be happy to.

I'm Twitter-less so will need your email.

Happy to chat you through the whys, what I found etc. also.

Would be my thanks for your site, which I enjoy each week. It's good stuff. So happy to help and swap ideas etc.

Cheers, d

Troy Wheatley said...

Awesome - thanks!

Troy Wheatley said...

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