Ranking System Explained

We get this question a lot, you will never find a ranking solution that will satisfy all parties and we have had some rather interesting conversations over the last season. We felt it prudent to explain how our system works and let us not understate the fact there is NO perfect system that exists.

While we tried a grading system based on points and allocating teams categories and while it worked we felt that there were issues in scaling up and including as many schools as possible. We therefore put our money where our mouths are and explored which rating system would work best for us and purchased software in order to hasten the process thereby allowing us to include far more teams.

The rating system we felt best would reflect the rankings for school rugby was the ELO Rating System.

The ELO rating was invented by Arpad Elo and it’s use has mainly been in chess. However the system has been adapted for use in American Football, Rugby League and since the end of the 2018 World Cup FIFA have used ELO as their ranking system.

ELO is used to predict the outcome of a game essentially, when two teams/players of an equal score face off against one another it is expected that should they play on multiple occasions they would win an equal number of times.

OUR METHODOLOGY

We base our pre-season rating on what is referred to as “Strength of Schedule”. Schools are pooled into groups based on the strength of the opposition they will be playing, their home and away schedule and the potential of the team based on their previous results.

Schools are assigned points and placed into pools as follows:

Pool A: 10 schools assigned a preseason rating of 1,490

Pool B: 20 schools assigned a preseason rating of 1,440

Pool C: 20 Schools assigned a preseason rating of 1,400

Pool D: 30 Schools assigned a preseason rating of 1,300

Pool E: 20 Schools assigned a preseason rating of 1,100

Pool F: The rest of the schools on our charts assigned a preseason rating of 900

As the season progresses ELO ratings change, thus what may be deemed a Category B team at the start of the season could end up losing 5 fixtures on the trot and thus could move into a Category C team thus decreasing their winning odds.

If for example Team 1 is ranked Category A and they secure a win over a category C team they will be assigned far lower points than beating a Category A team, in the same breath a Category C team beating a Category A team will see them gain significant ELO points.

The season is dynamic and thus ratings and Categories will continually change hands until the end of the season.

ELO IN PRACTICE

If we take a look at when we first started the ELO system with the South African school season in 2022 we can show examples of various fixtures and how it effected each teams Elo score.

TOP TIER: GREY COLLEGE VS PAARL GIM

At the time of this fixture both schools had sublime seasons and were among the top 2 in the nation, Grey at the time were ranked 1st with an ELO rating of 1,517 with Paarl Gim 1,509. The odds were 51% in Grey’s favour for this fixture but it was Paarl Gim who ended up victorious 22-17.

After this result Paarl Gim gained 15 points and Grey College lost 15 points with the post ELO rankings moving Paarl Gim into first position with Grey moving to second. A 51% chance and a score margin of 5 shows you how effective this rating system can be.

THE UPSET: RONDEBOSCH VS PAARL BOYS

The game started off with Rondebosch having a rating of 1,364 and Paarl Boys 1,508. The odds dramatically changed because of the difference in rating with Paarl Boys having a predicted 69% chance of a win.

We know the result, Rondebosch defied the odds and beat Paarl Boys securing 21 points with Paarl Boys losing 21 points and Rondebosch marching into the Top 10 while Paarl Boys moved down from 3rd to 5th.

 

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