Got some more updates ahead of season 2018:
- Pre-season Tracking: We had something resembling a normal preseason this year, so Squiggle is using those results in its calculations for the season ahead.
- Round-based Sensitivity: Squiggle is now more sensitive in the early rounds and in finals, to better capture the important signalling of surprising results at these times. In particular, an unexpected Round 1 result can cause a team to move a very long way.
- Goal-kicking Accuracy: As flagged last year, since goalkicking accuracy seems to be non-reproducible — teams that are highly accurate one week aren’t more likely to be highly accurate the next — Squiggle will interpret a scoreline like 13.20 as a team that was unlucky to not win by more, and thus will rate them more highly, while a scoreline like 12.3 will be interpreted as a team that got closer than they probably deserved.
- Home Ground Advantage: Gone is the practice of assigning 12 points of home advantage to interstate hosts and ignoring everything else! Squiggle now calculates HGA based on relative ground & state familiarity: It scores each team on how many times they’ve played at the same venue and (less significantly) in the same state over recent years, and assigns HGA points based on how lopsided the numbers are. So at venues where both teams have played fairly often, ground familiarity is balanced and there’s not much HGA, if any. At venues where one teams plays a lot and the other team rarely even visits the state, HGA is high.
The main difference in practice is better modelling of Geelong in Melbourne, along with uncommon situations like Melbourne playing in the Northern Territory. For example, for the Round 1 Melbourne vs Geelong game at the MCG, under the old model Squiggle would give Melbourne 12 points of HGA, but under the new model, it’s only 2.5 points, due to the Cats’ fairly good familiarity with that ground.
Actually here are the current HGA values for all R1 matches:
- Richmond +1.1 vs Carlton @ MCG
- Essendon +7.9 vs Adelaide @ Docklands
- St. Kilda +7.6 vs Brisbane @ Docklands
- Port Adelaide +10.0 vs Fremantle @ Adelaide Oval
- Gold Coast +10.3 vs North Melbourne @ Cazalys
- Hawthorn -1.0 vs Collingwood @ MCG
- GWS +9.0 vs Bulldogs @ UNSW Canberra
- Melbourne +2.5 vs Geelong @ MCG
- West Coast +10.9 vs Sydney @ Perth Stadium
Hawthorn are the only home team to have negative HGA. West Coast still get a bunch of HGA despite playing on a brand new ground due to the state-based numbers.