AFL Finals - more than a numbers game

We've been distracted by other matters, but we've suddenly regained our keen interest in the AFL. Of course, this has nothing to do with the Saints' great win over Geelong in the Qualifying Final. (And yes, that was a push in their back!)

Victorian teams have dominated this season. That's been very pleasing for traditionalists like us, who regard the AFL as the VFL + Interlopers. More pragmatically, it means that the top Victorian teams will not face an interstate final.

It is commonly believed that an interstate final spells doom for a Victorian team. Certainly, Hawthorn and Carlton fans are unlikely to take issue with this belief. But is it generally true? And do traveling non-Victorian teams typically fare any better? Fremantle and Sydney fans may be sceptical.

The interstate expansion of the VFL began in 1982, when South Melbourne moved to Sydney. The first final involving a non-Victorian team occurred in 1986, when Carltonbeat Sydney by 16 points. Notably, the game was played at the MCG, even though Sydney's higher ladder position should have entitled them to a home final; in those days, the interlopers were definitely treated as interlopers.

The West Coast Eagles were the first non-Victorian team to win a final, against Melbourne at Waverley in 1990. The Eagles were also the first non-Victorian team to host a home final, the following year when they were beaten by Hawthorn at Subiaco. It then took another ten years before a Victorian team won a final interstate.

There have been 94 finals between a Victorian and a non-Victorian team. There was one draw, and the winners of the other 93 finals are summarised in the following table. (We've gathered this data from the terrific website http://stats.rleague.com)

What does this table indicate? The home team has certainly won more often: 67 out 93 finals, a 72% success rate. However the home team has also usually been the higherranked team, and so it may be simply a case of the stronger teams having won. Indeed, the higher ranked team has also won 67 times.

It's difficult to separate the two factors. There have only been fourteen finals in which the traveling team - always non-Victorian - was ranked higher, and they won half of them. Not a bad record, but very little data.

However, we can also compare the results of Victorian and non-Victorian teams as home favourites. As the higher ranked home team, Victorian clubs have won 33 out of 45 finals, a 73% success rate. That's pretty good, but the non-Victorian clubs as higher ranked home team have won 27 out of 34 games: a 79% success rate.

So, when traveling, a lower ranked non-Victorian team has a little more than 1 chance in 4 of winning, whereas a lower ranked Victorian team has about 1 chance in 5. It's not a hugely significant difference, but it is clear which record is preferable. It is also probably not surprising: non-Victorian teams have more experience playing interstate games.

And of course, at the moment it is most preferable of all to be a fan of St. Kilda or Collingwood.

Puzzle to Ponder: Feel free to suggest solutions in the comments section. Please also email us if you wish to be added to our email list.

Next year, the Gold Coast Suns will be the newest interloper in the AFL. Suppose the Suns top the ladder, and are the only non-Victorian team to make the finals. They win their two home finals, and then win the Grand Final at the MCG. What would the above table then look like? What percentage of their games would higher ranked non-Victorian teams have won?

Burkard Polster teaches mathematics at Monash and is the university's resident mathemagician, mathematical juggler, origami expert, bubble-master, shoelace charmer, and Count von Count impersonator.

Marty Ross is a mathematical nomad. His hobby is smashing calculators with a hammer.