2019 Update
2018 in Review
So if indicators suggested 2017 was one of the best seasons in recent times, how did 2018 measure up? In a word, ordinary. Using some of the same metrics as last time around, we see that 2018 was unremarkable in many ways. That WA footy got a new home at Perth Stadium was probably the only non-team-specific highlight.
One of our major metrics was “salivating” contests, teams playing each other with similar amounts of game points-to-date, close to each other on the ladder. Below is the distribution of matches in terms of points differential. We see that 2018 was just an average year, unlike 2017. There was a nice spike of matches with 4 points differential but there was also a long tail matches with large points differentials, matches that we would usually presume to be foregone conclusions. The points difference between teams was 12.6 on average in 2018, ranked 79th over all 122 seasons. 2017 was ranked 13th in comparison.
Figure 1: Recent distribution of difference in points between the home team and away team prior to the match. The first quarter of the season is excluded to allow enough time for the competition to settle.
Round by round, things were also decidedly unextraordinary with 2018 being right on the average of the last 6 seasons. Round 21 wasn't too bad but the dud rounds started early than usual, from round 14 onwards.
Figure 2: Mean difference in points each round. The first quarter of the season is excluded to allow enough time for the competition to settle.
And as for blockbusters, two top 8 teams playing each other separated by no more than 2.5 wins, there were 25 of them in 2018, 2 less than 2017 and 2016. Seems OK but if we look at Friday nights, 2018 was poor with only 2 blockbusters, Sydney vs West Coast in round 13 and Port Adelaide vs Melbourne in round 14.
Figure 3: Blockbusters by round by season. The first quarter of the season is excluded to allow enough time for the competition to settle.
2018 also had 4 Friday night stinkers (a stinker being when the difference between teams is 4.5 wins or more). Round 11, Sydney vs Carlton, Round 18, St. Kilda vs Richmond, Round 21, Essendon vs St. Kilda and Round 22, Richmond vs Essendon. While we might have moaned about it in 2018, this is the norm in recent history. The good news is that St. Kilda and Carlton have been banished from Friday nights for the 2019 season.
Figure 4: Friday night stinkers by round by season. The first quarter of the season is excluded to allow enough time for the competition to settle.
Finally, how often did an upset occur? I defined an upset as when the home team gets up despite having 3.5 wins+ to date LESS than the visiting team (from round 6 onwards). This situation occurred 28 times in 2018, and the home team got up 6 times (21%). This was the worst result since 2003 but only 41st worst of all time. So not too bad. Remember these?
Brisbane defeated Hawthorn in Round 9 by 56 points at the Gabba
Bulldogs defeated Geelong in Round 15 by 2 points at Docklands
Adelaide defeated West Coast in Round 15 by 10 points at the Adelaide Oval
GWS defeated Richmond in Round 17 by 2 points at Homebush
Fremantle defeated Port in Round 17 by 9 points at Perth Stadium
North defeated West Coast in Round 19 by 40 points at Bellerive Oval
The other way round is where the away team gets up despite the home team having 3.5 wins+ than the away team. This occurred 30 times in 2018, with 6 upsets. (20%). This rate of winning was actually quite good, only bettered 26 times in history. Remember these encounters?
Essendon defeated West Coast in Round 14 by 28 points at Perth Stadium
St. Kilda defeated Melbourne in Round 15 by 2 points at the MCG
Brisbane defeated Fremantle in Round 15 by 55 points at the Perth Stadium
Brisbane defeated Hawthorn in Round 17 by 33 points at York Park
Gold Coast defeated Sydney in Round 17 by 24 points at the SCG
Bulldogs defeated North in Round 21 by 7 points at Docklands
Move over Geelong, Brisbane are the Hawks new bogey team.
So if 2018 was just another ordinary season, how did it translate into match attendance?
With the help of the new Perth Stadium, average attendance per match in 2018 was 30,817, which was 807 more than in 2017. However, if we exclude West Coast and Fremantle from the comparison, attendance actually decreased by 2%. Not a great outcome for the AFL.
While we see that improved match day performance meant that Melbourne, Brisbane, and Collingwood had good gains, Carlton, St. Kilda, and Western Bulldogs lost many fans at their games. That GWS also lost fans might also have the AFL concerned. North is also now a significant volume of fans below their Victorian counterparts. It is difficult to see how their Tasmania strategy will sustain the club over the long term.
Figure 5: Year-on-year change in home team match attendance.
Improvements in Predicting Match Attendance
This time last year, I had managed to get prediction accuracy, RMSE, of 5,810 with an SVM Polynomial algorithm. RMSE means that my predictions for home many people would attend a match were within plus/minus 5,810 people around two-thirds of the time. A promising result but not as good as I’d hoped (+/- 3,000 would be ideal).
The first improvement one can attempt with any model is to add more observations. And so with the addition of matches from the 2018 season, the RMSE was 5,803. No change. In some ways this is a comforting insofar as the model’s level of accuracy is predictable from year to year, that whatever dynamics it captured in crowd attendance between 2006 and 2017 also applied in 2018.
Last year, I thought a potential improvement was to add weather to the model, thinking that cold, rainy days might have a large impact on attendance. I therefore added "daily maximum", "daily minimum", and "daily rainfall" for nearby weather stations to the model. Unfortunately, this did not add much predictive power overall with a slight reduction in RMSE to 5,599. It turns out that weather has only a small impact on match attendance.
Disappointed, I started to look more closely at where the model was not doing very well with predictions and made three more tweaks. One was to flag "marquee" games such as Dreamtime at the G, and Anzac Day, games that might draw a crowd regardless of how teams match up. I also flagged derbies for a similar reason. After making these adjustments, the RMSE came down to 5,230, a small improvement.
It's a reasonable model and is getting close to being good enough to figure out how many pies to put in the oven. Perhaps by next season, I’ll have more ideas for improvements. It’s also possible that this is as predictable as match attendance will ever be.