October 18, 2019

Week 5 Ivy League Football Elo Ratings

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New this week, The Sun will release a weekly analytic-focused rating system for Ivy League football. The system, called Elo ratings, was originally developed to rank chess players by chess master Prof. Arpad Elo, physics, Marquette University, but has since been adapted and used in various sports to rank teams.

How it works:
Elo is a simple model that assigns each team a rating. A rating of 1500 represents an “average” team and higher ratings represent stronger teams. The ratings change each week based off of the final game scores. If a team wins, they will always gain Elo rating and if they lose, they will always lose rating. Also, the change in rating is only dependent on the opponent’s strength and the margin of victory or defeat. At the end of each season, there is a soft-reset of scores that allows the model to adjust for season turnover, but still factor in historical strength. The ratings can then be used to give win probabilities and point spreads for any game between two Ivy League teams. The formulas used and further explanation of the base model can be found in this FiveThirtyEight article, which uses a similar formula and method to create NFL Elo ratings.

Below is a graph of all eight teams’ ratings from this season and last season. The ratings only account for conference games, which is why some teams have only played one game and others have played two this season. Looking back at last year, it is clear that Princeton — the Ivy League champion — was the conference’s best, with a rating near 1700. It’s also apparent how poorly Cornell finished out the season, maintaining a dismal Elo rating that hovered around 1400 and put the team above only last-place Brown. The beginning of the 2019 season has seemingly brought more of the same. There have only been six conference games played so far, but it seems like last year’s trends may be continuing into this season.Screen Shot 2019-10-18 at 5.06.25 PM

Elo projections for this week’s upcoming Ivy League games point to a likely victory for Princeton over Brown and a near pick-em between Penn and Columbia.

Entering the fourth week of Ivy League play, Dartmouth and Princeton lead the rankings with identical ratings of 1647. Cornell is in second-to-last place with a rating of 1387 and — like last season — lead only Brown, which has a historically low rating of 1308. Cornell doesn’t match up against another Ivy League team this week, but faces the lowly Bears next Saturday.

Princeton at Brown — 12:30 p.m. Saturday
Princeton 84 percent chance of victory

This matchup has all the makings of a blowout. Princeton has not lost to an Ivy League team since week seven of the 2017 season and continues to sit atop the rankings with a rating of 1647. On the other side, Brown sits in last with a rating of 1308. Brown has actually been the lowest-ranked team in terms of Elo rating since week three of 2017 and has not been able to beat any Ivy League opponent since 2016. The model favors Princeton by 12.4 points, which is most likely an underestimation. Don’t expect an upset in Providence this weekend.

Penn at Columbia — 1:30 p.m. Saturday
Columbia 53 percent chance of victory

The second Ivy league game this week is a contest between Penn and Columbia in New York City. Columbia and Penn both had mediocre seasons last year finishing ranked sixth and fifth in Elo, respectively. Penn currently has a rating of 1482 and Columbia is at 1455. As the home team Columbia benefits from the model’s 30-point homefield rating boost to make the two ratings nearly identical. The model’s point spread on this game is less than .1 points and their win probabilities are almost 50/50. This figures to be a tight game and is the closest matchup so far this season.