Football is the most popular sport in the US, and most NFL fans watch the games with friends. Having studied NFL fans in the past and with #FriendsDay occurring during Super Bowl week this year, we were curious to turn our attention to studying the friendships between football fans. We took all people on Facebook in the US who have liked exactly one of the 32 NFL team pages as of September 1 (about 35M fans, out of nearly 50 million total fans of NFL team pages) and looked at patterns in the three billion friendships they share. All the analyses below were conducted on anonymized and aggregated data.

NFL fans have a lot of friends

First we looked at average degree of NFL fans to see which fans have the most friends. It’s not surprising to see Saints and Falcons fans, people from two famously friendly cities, at the top of the list. Turning to this year’s Super Bowl teams, we see Panthers fans have over 100 more Facebook friends than Broncos fans on average.

Friendships between NFL fans

Next we measured the fraction of those Facebook friendships that were with other hardcore NFL fans. At the top of this list we see people from some of the biggest football towns — Baltimore, Green Bay, and New Orleans. For fans of the Baltimore Ravens, an amazing 28% of their friendships are with other people who are loyal to one NFL team.

Fan friendships form near key off-season events

When do these NFL fan friendships form? People make new Facebook friends all year round as they meet new people or connect with old friends. We were curious to see if NFL fan friendships formed around certain times or events. We counted the number of new Facebook friendships formed per day between NFL fans, normalized the scale, and plotted it over the past year:

For a fan of the NFL, the patterns in this plot are pretty clear, but we added some annotations to highlight the large spikes. Right before the Super Bowl, the Combine, the Draft, the Preseason and the Regular season are the top times for people to form friendships. We also see a lull in new fan friending between the end of the Draft and the beginning of Training Camp.

NFL fans have surprising diversity in their fan friendships

We might assume that most of those fan friendships are between fans of the same team, but the data tell us otherwise:

There are only seven teams whose fans root the for same team as the majority of their friends on average. A few of these seven teams’ high rate of same-team friendships is likely due to geographic isolation, but it could also be driven by what social scientists call homophily, the tendency for people to meet and form friendships with people who have similar tastes and interests.

Turning to the bottom of the list, fans of some teams exhibit surprisingly low proportions of friends who like the same team. The average fan of the Jets could find it hard to watch the game with other Jets fans since fewer than 15% of his or her NFL fan friends like the same team. It’s worth pointing out that these numbers only hold on average. There may be plenty of Jets fans out there where large fractions of their fan friends also like the Jets.

Two notable teams at the bottom of the list are the Rams and Raiders — both teams who were moved from Los Angeles in the 1990s. Since many of these teams’ fans still reside in Los Angeles, they have substantial opportunities to meet and befriend fans of other teams.

Geography explains which team friendships are most likely

Only 41% of fan friendships are between fans of the same team. What determines the remaining 59% of friendships? Geography could play a large role by determining who people meet and become friends with.

The following map shows the one city containing the most fans for each team. We then overlay the most important friendship “edges” between each city selected by taking the top three city-pairs by number of friendships between the cities. Large cities like Chicago and Atlanta have more than three edges because they are are in the top three city-to-city friendships for many other cities. (We place the Raiders in Los Angeles, where there are slightly more single-team fans than in Oakland).

We can see some geographic clustering and in general graph distance and geographic distance are correlated. The West coast teams form a small clique which is mostly distinct from the other cities except for connections to Chicago and New York. Unsurprisingly because of their close proximity, the East coast cities are also highly connected. Certain cities form hubs, Chicago and Atlanta connect the Midwestern and the Southern teams respectively.

An update to the Facebook NFL Map

Of course NFL fans aren’t exclusively located in their home cities, they are spread out geographically. We updated the popular choropleth map to show a new perspective on how NFL fans are geographically dispersed (high quality png or svg):

In this map, the circles are centered around the 250 largest US cities by number of NFL fans and their areas are proportional to the number of fans in that city. We see a different picture than by using a county-level choropleth as a visualization. Large swaths of the old map were covered with team colors despite very few fans (and people in general) actually living in those areas.

Probably the biggest revelation is that some teams’ fan-bases are dominated by one very dense city (e.g. Bears or Eagles) while others are more dispersed across many smaller cities (Saints or Cowboys, who stretch as far west as Las Vegas). Sadly the Jets are still covered up by the Giants.

Who’s rooting for the Panthers and the Broncos?

Just like back in 2013, we can use the data on fans and their friendships to estimate where the support for the Super Bowl teams is coming from. First we can visualize where the US-based Broncos and Panthers fans live:

It’s not surprising to see the Broncos fans more spread geographically because they are an older, more popular team. But we see pockets of Panthers fans (often overlaid on larger pockets of Broncos fans) in large cities like Philadelphia, Houston, Los Angeles, and San Francisco.

But only about 6% of the 35M people we studied are fans of the teams playing in the Super Bowl. Who are the remaining 94% rooting for? If we assume a city will lend support to the Super Bowl team that it has the most fan friendships with, we get the following map showing friend allegiances for Sunday’s game:

Panthers fans draw their friends’ support from much of the Eastern seaboard, while the Bronco fans’ friends dominate the West Coast, Texas, and the rest of the South. It’s interesting to compare to the map we generated for last year’s Super Bowl matchup which more neatly divided the country.

Top Cities by Broncos Friendships

1. Houston
2. Los Angeles
3. Dallas
4. Chicago
5. Phoenix

Top Cities by Panthers Friendships

1. New York
2. Jacksonville
3. Philadelphia
4. Baltimore
5. Miami

Acknowledgments

Thanks to Neil Kodner, Ta Virot Chiraphadhanakul, Drew Margolin, Alex Walker, Jason Sundram, Shiu Pei Luu, and Robert D’Onofrio, (as well as many others I’m probably forgetting) for their help and suggestions! Plots were made using Hadley Wickham’s excellent ggplot2 library and Mike Bostock’s equally excellent d3 library.