2017 : Simulating the Final Ladder and Final Series After Round 21

Nine teams saw material changes to their Top 4 and/or Top 8 chances this week as the likely final ladder became just a little clearer, at least in parts.

Overall, this week's 50,000 simulations of the remainder of the 2017 AFL season sees:

  • six teams' Finals chances move by more than 5% points
  • five teams' Finals chances move by more than 10% points
  • five teams' Top 4 chances move by more than 5% points
  • four teams' Top 4 chances move by more than 10% points

(For details on the methodology I've used in the simulations, please see this blog.)


The charts below summarise the distribution of ladder finishes for the 18 teams from the simulations run after the current round, Round 21, and Round 20. Note that the ordering of the teams is slightly different in the two charts, reflecting improvement or deterioration in some team's expected ladder finish.



In terms of Final 8 chances, the big winners this week were:

  • Melbourne: +32% points
  • West Coast: +10% points
  • Port Adelaide: +7% points

The big losers were:

  • Western Bulldogs: -26% points
  • St Kilda: -17% points
  • Essendon: -11% points

In terms of Top 4 chances, we had as winners:

  • Geelong: +14% points
  • GWS: +11% points (up by 35% points now in the last three weeks)
  • Port Adelaide: +6% points

... and, as losers:

  • Richmond: -18% points
  • Western Bulldogs: -11% points

We see a lot more narrowing in the range of ladder finishes for almost every team this week, but there remains considerable uncertainty around the positions from 7th to 11th.



That uncertainty can be quantified by calculating Gini coefficients for teams and ladder positions (see this blog for some detail on what Gini coefficients are and how to interpret them).

Only four teams became less certain about their final ladder positions as a result of the weekend games (Brisbane Lions, Carlton, the Kangaroos and Hawthorn) and none of them because their hopes of playing Finals altered materially.

Most uncertain about their final ladder positions are the Western Bulldogs, Essendon, West Coast, and Richmond, the first three of those teams looking set to squabble over positions in the 7th to 11th range.

The teams enjoying the largest increase in the level of certainty surrounding their final ladder position were:

  • Melbourne - now over 60% likely to finish 7th or 8th
  • Port Adelaide - now over 60% likely to finish 5th or 6th
  • St Kilda - now almost 80% likely to finish 10th, 11th, or 12th
  • Western Bulldogs - now about 75% likely to finish 7th to 10th (though still the team whose position is overall most uncertain as noted earlier)

That fight for positions 7th through 11th is reflected in the Gini coefficients when we take a ladder finish perspective. Eighth is now the ladder spot with the highest level of uncertainty, but 9th and 10th have virtually identical coefficients.

The uncertainty surrounding every position except the bottom three shrunk this week, with the largest reductions coming for 6th and 7th positions. What raised the uncertainty levels for positions 16th, 17th, and 18th was the Lions' win over the Suns. 

1st remains the position about which there is most certainty, as it's almost certain that Adelaide will take it, while 14th is now the second-most certain position, with Fremantle about a 75% chance of occupying it.




Next, let's update the game importance table. It shows, you'll recall, how each team's chances of making the finals varies depending on the result of each of the remaining games. The overall Weighted Ave Importance figure tells us the average amount by which the teams' finals chances are expected to change on the basis of the outcome of a particular game. A larger figure means that the game is expected to change teams' finals chances, on average, by a larger amount and hence is a more important game.

(For more details about the methodology and the rationale for it, again please see this blog.)

The four key games for Round 22 are 

  • Gold Coast v Essendon
  • Western Bulldogs v Port Adelaide
  • GWS v West Coast
  • Melbourne v Brisbane Lions

All of these games have very significant direct implications for the participating teams who have genuine Finals aspirations, but also have non-trivial implications (ie 10% point changes in Finals chances, up or down) for other teams.

Of the remaining games, none are of any significant import in the context of the Top 8.


Next, an update on the analysis looking at how likely it is that a team will play Finals given that it finishes the home-and-away season on exactly 11, 11.5 or 12 wins.

Recall that these estimates, because they're based on a sample of simulations, are subject to error (as are all of those in this blog), which here is reflected in the width of the segment.

The upshot of this chart is that, to have at least a 50% chance of playing Finals requires:

  • No more wins: Adelaide, GWS, Geeelong, Richmond, Sydney, and Port Adelaide
  • At least 1 more win: Melbourne and West Coast (and only one win for them makes them virtually 50:50 propositions)
  • 2 more wins: Western Bulldogs and Essendon

St Kilda and Hawthorn, even with two more wins, remain less than 50% propositions for the Finals.

If we look, instead, at Top 4 finishes and winning between 13 and 14 games, we have the following.

In short, it remains the case that a minimum of 14 wins looks likely to be needed for a Top 4 finish. Amongst the current Top 5 teams, Richmond are least likely to finish in the final Top 4 if they finish on just 14 wins.

MOST LIKELY TOP 2s, top 4s, AND 5th to 8ths

This week we'll again look at the team orderings most likely for the Top 2 and Top 4 spots. But, with the increasing levels of certainty further down the ladder, we can also sensibly look at positions 5th to 8th.

Based on the latest simulations, the most likely final Top 2 remains Adelaide/GWS, which is now better than a 50:50 proposition.

Only five pairings appeared in any of the simulation replicates, and the fifth of those - Geelong/Adelaide - appeared in only a handful.

The most likely Top 4 remains Adelaide/GWS/Richmond/Geelong, which occurred in just over 17% of replicates. On first blush this seems odd, as the Tigers trail the Cats by half a game on the ladder and therefore need to win at least one game more than them to snatch 3rd spot. 

What confuses things, however, is that the Cats play the Giants as one of their two games, and the outcome of that game splits the various combinations where the Cats and Giants take 2nd and 3rd between them.

The ten most likely Top 4s shown here now account for almost 75% of replicates.

Looking next at the lower half of the Top 8, we find that a few orderings have become somewhat more likely than the rest, though none has emerged as a clear favourite.

Most common is a Sydney/Port Adelaide/Melbourne/Western Bulldogs finish, which occurred in about 4% of replicates.

The nine other orderings shown here each account for about 1.5% to 3% of replicates, and all 10 account for just under 25%. 

There is, still, much to be decided in this part of the ladder.


Applying the methodology as described in this blog to the 50,000 final ladders produced by our original simulations yields the following results.

It really is now a race in six for the Flag, with Melbourne, West Coast, the Western Bulldogs and Essendon, combined, accounting for only 5% of replicates. It remains the case though that a team from outside the Top 4 wins the Flag in 18% of replicates, and a team from outside the Top 4 finishes as Runners Up in 21% of replicates. As well, almost 4% of replicates see both Grand Finalists coming from outside the Top 4.

Adelaide are now even more heavily favoured by the simulations to take out both the Minor Premiership (95% chance) and the Flag (35% chance). GWS have about a 5% chance for the Minor Premiership and a 15% chance for the Flag, while Richmond, Geelong and Sydney all have about 11 to 14% chances for the Flag. Port Adelaide's Flag chances have increased a touch to around 6%.

We see from the heatmap above that, if we define the season in terms of the six events listed there, the most-likely finishes for each team are estimated to be:

  • Win Grand Final: Adelaide
  • Lose in a Preliminary Final: GWS, Richmond and Geelong
  • Lose in a Semi Final: Sydney
  • Lose in an Elimination Final: Port Adelaide and Melbourne
  • Miss the Finals: all other teams

We also see that Adelaide are estimated to be about 57% chances for making the Grand Final, GWS about 33%, Geelong and Sydney about 29%, and Richmond about 24%. Port Adelaide are now about 15% chances and Melbourne about 5% chances.