The race for ranking points and a good RWC draw

A simulation-based look into the next few months of international rugby

Since the end of the British & Irish Lions tour, there has been more discussions of the Rugby World Cup, and in particular of the upcoming draw. Let’s look at what the data can tell us.

What has changed?

The 2027 Rugby World Cup will be the first one to include 24 countries (up from 20 countries previously). The competition will now involve six pools, as well as a Round of 16 before the quarterfinals.

For most Tier-1 nations, getting out of the pool should not be a problem. The presence of a Round of 16 means that the top two teams from each of the six pools and the four best third-placed teams will have to go through to the playoffs. It is not a high bar. However, being one of the best eight teams reaching the playoffs is crucial to getting an easier game. That means winning the pool, or at least doing well enough to be one of the two best second-placed teams.

The draw will take place in December, with the seeding based on the World Rugby rankings at the time. For the best teams, a spot in the top 6 is very important. Similarly, for a team like Wales, staying in the top 12 is essential to avoid a nightmare scenario where they could for instance be in a pool with South Africa and Argentina (based on current rankings).

How do the rankings work?

The World Rugby rankings are based on game outcomes. Every time a game is played, a point exchange is calculated. The value for that point exchange depends on the ranking points for the two teams before the game and on the point difference at the end of the game. The process is explained on the World Rugby website, but a few things are worth highlighting.

First, scores matter. If a team wins by more than 15 points, the point exchange is increased by 50%.

Second, a win for a team that is more than 10 ranking points higher than the opposition does not lead to any point exchange.

Finally, home advantage matters. The home team receives a bonus of 3 points in the calculation. For instance, if a team is sitting on 82.37 points and is playing at home, the point exchange is calculated as if they actually had 85.37 points.

The last two points come together to impact next weekend’s games:

• South Africa currently has 92.78 points, and Australia 82.08. Australia therefore cannot lose any ranking points this week. They can only gain points (with a draw or a victory) or stay at the same level.

• Argentina is also just over 10 points below New Zealand (10.01, 82.05 vs 92.06), but because they are playing at home, they are treated as if they had 85.05 points. If they lose, they will lose ranking points.

Endless permutations

Based on the explanation provided by World Rugby, it is relatively easy to calculate how one game, or a few games, could impact the rankings. There are even some tools to help you, such as this one.

Jonathan Drennan has written a very interesting article looking at some games for Australia, and how they impact the Wallabies’ chances of a top-6 seeding.

However, it quickly becomes difficult to look at several games: the results of one game will impact the ranking points and therefore the potential point exchange of any game taking place later. Manually keeping track of all the permutations is not very practical.

I have written a simulation tool that takes the current rankings and allows the user to provide predictions for future games. Rather than a unique prediction, the user gives the probabilities for all possible outcomes: team A winning by more than 15 points, team A winning by up to 15 points, a draw, or team B winning by up to, or more than, 15 points.

The tool then simulates a number of alternate futures (think multiverse, but for rugby), in which the outcome of each game is randomly generated using these probabilities.

What will the rankings look like in December?

I had a go at providing some probabilities for 42 upcoming games, and ran 100,000 simulations. I then looked at the distribution of possible ranking points for each team. The results for the teams currently ranked 1-14 are shown in the violin plot below.

An interesting thing to note is that everything is still at play. Points can fluctuate a lot, especially for teams that have a lot of games still to play (such as the four about to embark on the Rugby Championship).

I also looked at which teams make the top 6 by December. Unsurprisingly, teams like South Africa, New Zealand, Ireland and France are fairly safe, but the battle between Argentina, Australia and (to a much lesser extent) England looks very close.

For anyone wondering, I also have Wales hanging to a top-12 ranking just under 61% of the time.

For good measure, I also looked at who is the top ranked team. There is not a lot separating South Africa and New Zealand.

Of course, all these results are based on the probabilities I have provided. I do not think they are outlandish (I tried to find a balance between being conservative and still having upsets that shake up the rankings), but feel free to download the tool and run it with your own predictions. If you get very different rankings, please share them in the comments!

The tool is here: https://github.com/SystemsResearch/ranking_calculator