2019 - Team Ratings After Round 13
/With the teams second and third on the Ratings ladders - viz, the Pies and the Cats - both having a bye this weekend, GWS had the chance to extend its lead over the pair, which it did under MoSHBODS but not under MoSSBODS where a 3 scoring shot victory was deemed to be insufficiently large to justify the estimated pre-game difference in abilities.
Nonetheless, GWS still holds a 1.4 scoring shot lead over Collingwood on MoSSBODS, and a 4.5 point lead over Geelong on MoSHBODS.
In stark contrast with last week’s major reshuffling, only five teams moved rankings on MoSSBODS this week, and only Fremantle by more than a single spot, while just seven moved rankings on MoSHBODS, including only Port Adelaide, North Melbourne and Fremantle by more than a single spot.
Those moves left the Systems now differing in their rankings of only four teams by more than two spots:
Port Adelaide, ranked 4th by MoSSBODS and 7th by MoSHBODS
Melbourne, 7th and 12th
Adelaide, ranked 10th and 5th
Western Bulldogs, ranked 11th and 14th
West Coast, ranked 14th and 9th
Whilst some of those differences might seem large, it’s important to bear in mind that team rankings are determined by quite small differences in absolute ratings in some cases. To illustrate this, note that the gap between 5th and 8th on MoSSBODS now stands at just 0.4 scoring shots, and between 5th and 13th at just 1.9 scoring shots. Similarly, the gap between 5th and 8th on MoSHBODS is just 1.9 points, and between 5th and 12th just 6.2 points.
As such, comparing raw rankings across the two Systems can tend to exaggerate the true underlying differences in their assessment of ability. In fact, the correlation between team ratings on the two Systems stands at +0.96.
Also, only two teams are rated above-average by one of the Systems and below-average by the other: Melbourne and West Coast.
You can see how broadly similarly the two Systems have rated all 18 teams this season by watching the animation below, which displays, side-by-side, the Systems’ round-by-round team ratings.
On the Component Ratings we see no changes in the Top 3 on offence or defence for either System this week.
On MoSSBODS, 6 teams are now rated positively on offence and defence (up 2), 5 are rated negatively on both (up 1), 2 are rated positively on offence but negatively on defence (down 1), and 5 are rated negatively on offence but positively on defence (down 2).
Three teams are in different quadrants under the two Systems:
Essendon (positive offence and defence on MoSHBODS, negative offence and positive defence on MoSSBODS)
West Coast (negative offence and defence on MoSSBODS, negative offence and positive defence on MoSHBODS)
North Melbourne (positive offence and defence on MoSSBODS, positive offence and negative defence on MoSHBODS)
Looking across all 18 teams we find that:
on offence, only West Coast is ranked more than 2 spots differently by the two Systems
on defence, six teams are ranked more than 2 spots differently by the two Systems (Port Adelaide, Essendon, Melbourne, North Melbourne, Adelaide, and West Coast).
Next, let’s compare each team’s current ratings with those of teams from the past at the same point in their respective seasons (ie after 13 rounds of the home-and-away season).
Teams shown as red points are teams that eventually finished premiers, and those shown in orange finished as runners up.
GWS remains the only team with a Combined Rating above the median for all previous Grand Finalists at this point in the season, and Collingwood, Port Adelaide, and Geelong the only other teams with Combined Ratings above the lowest decile for all previous Grand Finalists. Carlton and Gold Coast both still have Combined Ratings lower than that of any previous Grand Finalist at this point in the season.
If we focus purely on those seasons from 2000 on, we obtain a similar picture except that GWS falls slightly below the median.
The following animation shows the path that each team has followed, at the end of each round, to get to its current rating, and shows how small the typical changes in ratings were this week.
GWS did enough to grab 2nd on ChiPS this week, and significantly reduced the gap to Collingwood in 2nd on MARS where they now trail by just 0.3 Rating Points.
Just five teams moved spots on ChiPS, most notably Essendon (up 3 spots to 6th) and Hawthorn (down 4 spots to 10th), while only three teams moved spots on MARS, and none by more than two spots.
That’s left the two of them disagreeing about the ranking of Richmond, Sydney, Adelaide, and West Coast by more than two places.
As for the MoS twins, however, a comparison of ChiPS’ and MARS’ team rankings tends to overstate the underlying differences in assessed abilities. The correlation between ChiPS’ and MARS’ Ratings currently stands at +0.97.
Looking across the rankings of all four Systems and ordering the teams based on the current competition ladder (as we define it based on competition points per game played with percentage the tie-breaker), we find that:
Sydney now has the widest range of rankings (from 5th on ChiPS to 16th on MoSSBODS)
West Coast has the next-widest range (from 5th on MARS to 14th on MoSSBODS)
Melbourne has the next-widest range of rankings (from 7th on MoSSBODS and 14th on ChiPS and MARS)
Adelaide has the next-widest range of rankings (from 4th on MARS to 10th on MoSSBODS)
Then come Fremantle and Port Adelaide (Fremantle is 8th on MoSHBODS and 13th on ChiPS, and Port Adelaide 4th on MoSSBODS and 9th on ChiPS)
No other team is ranked more than four places differently across the four Systems.
Gold Coast and Carlton are still the only teams ranked identically by all four Systems, but six other teams’ rankings cover only two or three values.
We now see fairly large positive differences between ladder position and Rating System rankings (ie three or four red dots, where Rating System ranking is much lower than ladder position) for only the Eagles, Lions and Saints, and large negative differences (ie three or four green dots) only for the Dons.
