How Does This Work?

• RugbyHawk rankings are based purely on objective algorithms, and all teams that have played a Division 1 game since 2021 are included in the rankings.
• The Elo ratings use game scores to determine each team’s true skill level. 1500 is considered average.
• The Pairwise Rankings use the Elo as well as head-to-head results to output current rankings.

Elo Rating System

The Elo rating system was created for chess and has been adopted for a variety of sports, including rugby. This site and this site help explain our implementation for Elo, and our code is on GitHub.

The primary features of an Elo system are:

• Teams gain rating points by winning and lose rating points by losing.
• The gained and lost rating points for each game are equal; it's an exchange of points.
• Teams gain more when beating higher rated teams and gain fewer when beating lower rated teams (vice versa for losing).
• Margin of victory impacts the points gained or lost, but the impact tapers off as the margin increases.
• Home victories earn fewer rating points than away victories (vice versa for losing).

All teams start at 1500, which is considered the average rating.

Our Elo rating system is based on a master’s research project by Northwestern University’s Marcus Thuillier as well as FiveThirtyEight’s National Football League Elo implementation.

Pairwise Ranking System (PWR)

RugbyHawk’s Pairwise Rankings emphasize head-to-head victories in order to determine which teams are “most deserving” of playoff selection. In the Pairwise, every team is compared against every other team, and the better team in each comparison gets a point. Teams are ranked by the total number of comparison points that they have.

Each comparison uses three criteria:

1. Head-to-Head Winning Percentage
2. Winning Percentage Versus Common Opponents
3. Elo Rating

The criteria are evaluated in order, and when either team wins a criterion, they are considered to have won the full comparison.

Our Pairwise Ranking system is tailored to college rugby, and inspired by USCHO’s version for college hockey.

What Games are Included?

We currently provide rankings only for Division 1 men’s college rugby. Games are only included if they are full length and between two schools' first sides. Games played by Division 1 teams against lower-division opponents are still included.

Eligible Teams

It’s only possible to give teams an accurate rating/ranking if there’s enough data of their games. More specifically, teams need:

• Enough Games: If a team has less than 5 games played, we don’t have a large enough sample.
• Connectivity to the Broader Network: We need to avoid bubbles of teams who have played enough games, but have only played each other.

If a team doesn’t meet our eligibility criteria, we still give them an Elo rating, but their starting rating is docked 200 points to 1300, since teams who don’t meet the criteria tend to be worse than teams who do. Additionally, ineligible teams aren’t included in pairwise comparisons, so they have pairwise scores of 0.

If your team isn’t eligible, you can help by digging up more game scores and reporting them here.

If your team doesn’t appear on this website at all, it’s because our records say they haven’t played any Division 1 games since Fall 2021.

The more games played, and the greater variety of opponents, the more accurate the algorithm will be. 15s rugby tends to have a low number of games, often against a small pool of opponents (each team’s conference). The rankings for teams who play in conferences with very few nonconference games should be used with less confidence than those for teams with a wider variety of opponents.

Who are We?

RugbyHawk is run by Matt Trenary and George Janke, and also features contributions from others involved with University of Michigan Rugby. The site's code and and its update history are public in order to eliminate any fear of favoring Michigan. Find our GitHub here.

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