Here's the table The Age published this morning from Jesse Hogan. See if you can spot the problem. It's supposed to be the aggregate of opponents' wins so far this year, but it actually covers the entire 23 rounds. But that's not what I mean:
179 Adelaide (easiest)
182 North Melbourne
185 Brisbane
186 St Kilda
188 Sydney
193 Fremantle, Richmond
196 Melbourne
198 Essendon
202 Carlton
204 GC, GWS
205 Collingwood
206 West Coast
207 Hawthorn
211 Geelong, Bulldogs
214 Port Adelaide (hardest)
That's a whopping 35 wins between easiest and hardest, right? The problem is obvious when you use the same method to calculate the fixture difficulty in 1986, the last time we had a double round robin:
228 Hawthorn (18 wins)
232 Sydney (16 wins)
234 Carlton
...
260 St Kilda (2 wins)
So in a completely unbiased draw, we still get a gap of 32 wins between easiest and hardest. WTF? The trick is that St Kilda's opponents have picked up 20 wins against the hapless Saints (and we count them as 40 because each one is played twice). To correct this biased indicator, we would need to subtract that number from the total and leave every team on a draw strength of 220. Make sense?
When we haven't got a full round robin, the maths is a little bit more complicated but the principle is the same. Here's the unbiased table for the full season on the same scale*:
210 North Melbourne
211 Brisbane
215 Adelaide, Melbourne
217 St Kilda
220 Richmond, Gold Coast
225 Sydney
226 GWS
227 Fremantle
(229 average)
233 Essendon
237 Carlton, Bulldogs
239 Port Adelaide
244 Collingwood, West Coast
246 Hawthorn
250 Geelong
Pre-season I rated Collingwood's draw as the toughest, and almost the toughest possible based on 2011's ladder. Based on this year's numbers, that throne has been taken by Geelong. To put that 40-win difference in perspective, it's like Geelong playing an opponent that is two wins (or about nine scoreboard points) harder than North's every single week. That's real fixture bias, and there could be a good case for thinking Geelong deserve a top-four spot more than Adelaide.
(* there is rounding involved here to take account of the mix of teams that have not played each other, or have played each other twice, so it's slightly different to just subtracting the number of losses)
179 Adelaide (easiest)
182 North Melbourne
185 Brisbane
186 St Kilda
188 Sydney
193 Fremantle, Richmond
196 Melbourne
198 Essendon
202 Carlton
204 GC, GWS
205 Collingwood
206 West Coast
207 Hawthorn
211 Geelong, Bulldogs
214 Port Adelaide (hardest)
That's a whopping 35 wins between easiest and hardest, right? The problem is obvious when you use the same method to calculate the fixture difficulty in 1986, the last time we had a double round robin:
228 Hawthorn (18 wins)
232 Sydney (16 wins)
234 Carlton
...
260 St Kilda (2 wins)
So in a completely unbiased draw, we still get a gap of 32 wins between easiest and hardest. WTF? The trick is that St Kilda's opponents have picked up 20 wins against the hapless Saints (and we count them as 40 because each one is played twice). To correct this biased indicator, we would need to subtract that number from the total and leave every team on a draw strength of 220. Make sense?
When we haven't got a full round robin, the maths is a little bit more complicated but the principle is the same. Here's the unbiased table for the full season on the same scale*:
210 North Melbourne
211 Brisbane
215 Adelaide, Melbourne
217 St Kilda
220 Richmond, Gold Coast
225 Sydney
226 GWS
227 Fremantle
(229 average)
233 Essendon
237 Carlton, Bulldogs
239 Port Adelaide
244 Collingwood, West Coast
246 Hawthorn
250 Geelong
Pre-season I rated Collingwood's draw as the toughest, and almost the toughest possible based on 2011's ladder. Based on this year's numbers, that throne has been taken by Geelong. To put that 40-win difference in perspective, it's like Geelong playing an opponent that is two wins (or about nine scoreboard points) harder than North's every single week. That's real fixture bias, and there could be a good case for thinking Geelong deserve a top-four spot more than Adelaide.
(* there is rounding involved here to take account of the mix of teams that have not played each other, or have played each other twice, so it's slightly different to just subtracting the number of losses)