It's a hallmark of ELO rating systems that their level of surprise determines the size of their rating response, and this week's results provides an interesting case study of this behaviour.
ChiPS expected Adelaide to win this week by 33 points, which turned out to be the exact margin of their victory, so ChiPS made essentially no adjustment to the Crows' rating. MARS, in contrast, expected the margin to be much narrower, and so rewarded Adelaide with a 2.4 Rating Point (RP) increase, enough to catapult it into 1st place on its ratings.
Adelaide was one of seven teams changing rank on MARS ratings this week, though Fremantle was the only other team to move by more than a single spot, sliding down two places into 12th.
Nine teams changed places on ChiPS ratings, including Collingwood, up three places into 11th, and Geelong, Fremantle, and Melbourne, each falling two places into 3rd, 12th and 14th respectively.
MARS now rates six teams above 1,020, an extraordinarily high number for this point in the season. At the same time last year, MARS rated only four teams this highly: Fremantle, Hawthorn, Sydney, and West Coast. ChiPS, by comparison, rates only three teams above 1,020 (noting that MARS and ChiPS Rating Points are not strictly equivalent), the same number that it did at the end of Round 14 in 2015.
In short, MARS considers the competition to be broadly less competitive at this point than does ChiPS, a fact you can also observe in the chart of current ratings.
ChiPS' and MARS' team re-rankings leave them most in disagreement about:
- Adelaide, ranked 1st on MARS and 5th on ChiPS
- GWS, ranked 6th on MARS and 2nd on ChiPS
- Hawthorn, ranked 3rd on MARS and 7th on ChiPS
- Melbourne, ranked 11th on MARS and 14th on ChiPS
The correlation between raw MARS and ChiPS ratings now stands at +0.985.
On MoSSBODS this week, 11 teams changed rank, including every one of the teams now ranked in MoSSBODS' top 7.
Adelaide slipped into 1st position, relegating Geelong to 2nd, while GWS took advantage of the Bulldogs' week off to nudge them back into 4th. West Coast and Sydney meantime benefited from a lacklustre Hawks showing, moving into 5th and 6th respectively as the Hawks fell to 7th.
Further down the order, Fremantle fell three places into 14th, allowing each of the three teams previously directly below them - St Kilda, Richmond and Melbourne - to move up a spot each.
On Offensive ratings, only five teams changed rank, and only one, West Coast, by more than a single spot. The Eagles rose two places into 5th as Hawthorn and the Kangaroos both slipped a place on the back of poorer-than-expected Scoring Shot production.
Defensive ratings were a little more dynamic, with a dozen teams altering rank including Collingwood's rising three places into 8th, Adelaide's climbing two places into 6th, Carlton's slipping three places into 12th, and the Kangaroos' falling two spots into 9th.
Set against the backdrop of history after Round 14s of every home-and-away season in V/AFL history, we have the following:
Adelaide and Geelong are clearly at the high-end of ratings for teams that eventually finished 1st or 2nd in their respective years, while GWS, the Western Bulldogs and West Coast are around about the median, and Hawthorn and Sydney are a little below that.
The remaining teams have Combined Ratings that would place them, at best, in the lowest 10% of all teams that subsequently finished in the top 2 for the year.
After all of its re-rankings this week, MoSSBODS now disagrees significantly with both MARS and ChiPS about the rankings of only two teams:
- The Western Bulldogs, ranked 4th by MoSSBODS, but 8th by MARS and by ChiPS
- Sydney, ranked 6th by MoSSBODS, but 2nd by MARS and 1st by ChiPS
Lastly then, here's an animation showing the Crows' ascendancy (and the ratings stories of every other team so far this season).