We usually assume that home field gives the host team a distinct advantage over the road team. In fact, announcers will usually talk about the disadvantage that a team has because they have to go on the road to play. However, when you look at the evidence, not every home field gives its team an advantage. Consider this:
1. There is no correlation overall from year to year for home records. In other words, many teams in the NFL that performed 3 games better at home than on the road one year, for instance, fare no better at home than on the road the next year.
2. When comparing each team's home record against each team's road record, there were 10 teams for which there was no statistical difference whatsoever. Those 10 teams, in other words, performed just as well on the road as they did at home. In fact, there are four NFL teams that actually perform better on the road than they do at home over the past five years!
Okay, so those points made, the are an additional handful of teams that over the past five years have enjoyed a consistent, moderate homefield advantage. Finally, there are an additional dozen or so teams that perform so much better at home than they do on the road, that these teams are considered to have the best homefield advantage in all of the NFL.
When trying to pick the outcome of a close matchup and you want to take homefield advantage into account, it may be wise to consult the table below. As you'll see, not all teams enjoy the same advantage at home. Let's break down the list and try to examine why some stadiums help their teams more than others.
First, here are the teams for which their home field does not help them at all. The number in parentheses in the margin by which their winning percentage at home is better than their winning percentage on the road:
Carolina Panthers= -10
New Orleans Saints= -8
New York Giants= -3
Philadelphia Eagles= -3
Tennessee Titans= 5
New England Patriots= 5
Dallas Cowboys= 5
Atlanta Falcons= 5
Indianapolis Colts= 8
Green Bay Packers= 8
A few observations:
1. As my wife actually pointed out, the Giants and Eagles being on this list is not surprising. I live in New York and she lived in Philly for four years, and fans of those two teams are, shall I say, brutal to their teams. Maybe this shows that constantly berating your own team may just have a negative impact on their performance.
2. New England and Indy also are not a surprise. Over the past 5 years, they've won so consistently on the road that their home record simply had little room to be much better.
3. Two myths shattered in one list- The Saints actually play worse in the Superdome than they do on the road. Plus, the vaunted Lambeau Field gives the Packers absolutely no discernible advantage over their visitors. Go figure.
4. Carolina fans, care to weigh in with a theory?
Next, the following teams enjoy a moderate advantage playing in their own stadium:
Miami Dolphins= 10
Washington Redskins= 13
San Diego Chargers= 15
Cincinnati Bengals= 15
Oakland Raiders= 18
Cleveland Browns= 18
St. Louis Rams= 18
Tampa Bay Buccaneers= 20
New York Jets= 20
Buffalo Bills= 20
Pittsburgh Steelers= 20
Observations...
1. Weather and geography, at first glance, don't appear to play much of a factor. There are just as many warm weather teams on the list as there are cold weather teams, and they seem to be spread around the country.
2. The Jets, who play in the same stadium as the Giants, enjoy a significant advantage at home, while the Giants are actually worse. In my opinion, it's always been clear that Jets fans have been more loyal than Giants fans (probably because they have to be). But can that really be the sole explanation? I'm open for suggestions.
3. The Redskins are the only NFC East team that actually has a homefield advantage. I'm not sure if I should make anything of that, or if it's simply weird.
Finally, here are the teams with a tremendous homefield advantage. Before looking, do you think you can guess #1?
Houston Texans= 23
San Francisco 49ers= 23
Denver Broncos= 23
Jacksonville Jaguars= 23
Detroit Lions= 25
Chicago Bears= 25
Kansas City Chiefs= 28
Minnesota Vikings= 28
Arizona Cardinals= 35
Seattle Seahawks= 38
Baltimore Ravens= 43
Observations...
1. First of all, just astonishment at that number by the Ravens. Playing with a winning percentage 43 points better at home than on the road, they are like two completely different teams.
2. Something Seahawks fans already know- As the playoff race gets tight, they must keep an eye on home and away game left, because at home they are excellent. On the road, they're not even in the top half of NFL teams.
3. I've read many times about how loud and unfriendly Arrowhead can be for visitors. Now I see empirical proof of it.
4. Now we know what it will take to turn around the Cardinals- more home games.
Big Changes Coming
10 years ago
3 comments:
Hi. Dig the site. Keep it up. Quick nitpick with the HFA analysis, however.
By your measure, what's the HFA of a 16-0 team? Home win% - Away win% = 0. So, the closer you get to 16-0 or 0-16, the smaller the HFA will naturally appear without really telling us anything about a team's true HFA.
So teams that have historically been mediocre, will tend to appear to have high HFA. Conversely, teams with consistently above average or below average records will appear to have a low HFA.
I've found HFA is pretty much the same in the NFL, except for probably GB and CHI. Because each have 2 division dome opponents and play in cold climates, they enjoy the (very strong) "dome at cold" effect more often than most other outdoor teams.
The rest is likely due to random variation.
To calculate HFA, I actually compared home wins and losses season-by-season instead of percentages, but the end result is the same.
As far as range restriction because of the great teams and the terrible teams having low HFA, I considered just that point. In fact, I mention it when explaining Indy and New England's low HFA ratings.
I tried to articulate, perhaps unsuccessfully, that the list does not imply that the top teams play best at home and the bottom teams play worst. Instead, the top teams show the biggest home-over-road improvement and seem to benefit most from playing at home.
Taking a sampling from a five-year period, I was able to get enough of a sample size to see which teams, through both their good years and bad, benefited most from home. Even with a team like the Colts, five years of sampling supplied enough Colts losses to demonstrate that they loses just as many at home as they do on the road. Another team that has been consistently good for five years, the Seahawks, clearly do far better at home.
It's true that most of the teams with disproportionately great home records are typically in the middle of the pack, but perhaps that has something to do with their inability to win road game? Who knows...
As for random variation, I would say that in some cases, that may be true, but when Baltimore or KC receive an ANOVA score like they did here, chance has to be considered a long shot.
Season-by-season percentages of home improvement would create the same illusion. It doesn't really matter how you measure HFA. I agree.
To clarify, teams that tend to have middling records *each year* within the 5-yr period (lots of 8-8s or 9-7s, etc.) will be the teams that appear to have strong HFA. Like you said, teams with disproportionately great home records tend to be in the middle of the pack. That's exactly what we'd expect.
It's not possible for the reason to be an inability to win on the road. If that were true, those teams could not be 'middle of the pack' teams. They'd be below-average.
Keep in mind that records can be slightly deceiving. Even though the Seahawks seem above average, they were within 2 games of .500 in 4 of the last 5 seasons, and they have been in an extremely weak division. Two games a year each against SF and ARI would easily account for any deviation above 8-8. My only point here is that Seattle has actually been a 'middling' team.
It's this way in every sport. I studied this for the NBA too, and the the effect is even more pronounced.
Regarding randomness, even if this were completely due to luck, which I'm not claiming, we'd still see 1 or 2 statistically significant results. If 1 out of 20 cases appear statistically significant although they're really not (type I error rate for p=0.05), then we'd naturally expect 1, 2, or more teams to falsely appear significant in any analysis.
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