Despite New Zealand’s recent loss to South Africa, statistical modeling suggests that the All Blacks are the favorites to win the 2023 Rugby World Cup. According to Rugby Vision, an algorithm developed to predict rugby competition outcomes, New Zealand has a 33.5% chance of winning their fourth Rugby World Cup title. The next most likely champions are South Africa at 26.2%, followed by France at 20.6%, and Ireland at 11.9%.
The evaluation of the model’s predictions in past Rugby World Cups shows that it is accurate. It’s well-calibrated, which means it provides reliable forecasts. While the model shares some similarities with the official world rugby rankings, it’s not as influenced by the results of individual games.
The Rugby Vision model relies on three main elements:
A rating system for international teams, which assesses their strength.
Estimation of expected outcomes for each Rugby World Cup game based on these ratings.
Running 10,000 simulations of the tournament to consider uncertainty and variations in expected outcomes. This helps account for unexpected results and fluctuations.
Global rugby rankings
The Rugby Vision rankings are a unique system that uses past game results and considers factors like home advantage when determining team rankings. After each game, if a team performs better than expected, they gain rating points, and if they perform worse than expected, they lose rating points.
The rankings and rating points for the 20 teams qualified for the 2023 Rugby World Cup are provided below.
It’s important to note that while the same four teams make up the top four in both the Rugby Vision rankings and the official rankings, the order may differ. Currently, the official world rankings place Ireland at the top, followed by South Africa, France, and New Zealand.
Predicting game results
In the Rugby Vision rankings, the difference in rating points between two teams equals the predicted score margin for a game played at a neutral venue. If there’s a home advantage, it’s worth 5.5 points.
For example, in the opening game of this year’s Rugby World Cup between France and New Zealand in Paris, New Zealand is expected to win by three points. This prediction is based on the difference in the teams’ rating points (128 minus 119.5) plus 5.5 for France’s home advantage.
This estimate means that if the game were played 100 times, New Zealand would win by an average of three points. According to the model, in those hypothetical 100 matches, New Zealand would win 57 games, France would win 40, and three games would end in a draw.
RWC simulations
In the Rugby World Cup, teams are first divided into four pools, and the top two teams from each pool move on to the quarterfinals.
During the pool stage games, teams can earn competition points based on their performance. They get four points for a win, two points for a draw, and there are two types of bonus points available. One bonus point can be earned if a team loses by seven or fewer points, and another bonus point is awarded if a team scores four or more tries in the match.
The Rugby Vision framework includes a model that predicts how many tries each team is likely to score in each game.
To handle the uncertainty in game outcomes, the system runs simulations of the Rugby World Cup 10,000 times, following the tournament rules. For each of these simulated tournaments, the framework calculates expected game results, bonus points for pool games, the final pool standings, results of knockout matches, and the winner of each knockout game.
The estimated probabilities of each team reaching different stages of the 2023 Rugby World Cup are displayed below. These probabilities are influenced by factors like team rating points, including any home advantage for France, and the draw, which determines which pool each team is in and the rules for assigning teams to knockout games.
Pool predictions and beyond
Here are the predictions for the Rugby World Cup pools and beyond:
In Pool A, New Zealand (98.9%) and France (97.9%) are very likely to qualify for the quarterfinals.
In Pool B, South Africa and Ireland are expected to reach the quarterfinals, but there’s a 26.3% chance that Scotland could upset one of them.
Pool C is quite competitive. Australia (87.2%) and Wales (68.3%) are the top contenders to advance, but Fiji (37.3%) also has a reasonable chance.
In Pool D, England and Argentina are the favorites for the quarterfinals, with Japan and Samoa as potential spoilers.
After the initial round, Pool A teams will face opponents from Pool B in the quarterfinals. Since these are strong pools, the chances of reaching the semifinals for these teams are relatively low.
For example, Ireland has an 81.2% chance of making it to the quarterfinals but only a 33.1% probability of reaching the semifinals.
Teams in Pools B and C will have relatively easier quarterfinal opponents. As a result, despite their lower rankings, England is the second most likely team to make it to the semifinals.
Towards the final whistle
As the Rugby World Cup progresses towards the final stages:
In the semifinals, teams from Pool A and/or B will face teams from Pool C and/or D. Since teams from Pools A and B are expected to perform well, their chances of reaching the finals are only slightly lower than their chances of making it to the semifinals.
Conversely, teams from Pools C and D, while having good chances of reaching the semifinals, have relatively lower probabilities of becoming finalists. For example, England has a 55.0% chance of reaching the semifinals but only a 9.7% chance of being in the final.
The tournament draw favors Pool C and D teams to reach the semifinals, but they are likely to face strong opponents in the semis. In short, the draw helps these teams progress further in the tournament but doesn’t necessarily increase their chances of winning.
While the Rugby Vision predictions offer a reliable forecast, it’s important to remember that upsets can occur in sports. That’s what makes sports so interesting, after all.
So, even with predictions, the outcome of the Rugby World Cup remains uncertain and exciting.
