How Strong is the 12th Man? A Study in Home Field Advantage
Aug 11, 2012; Seattle, WA, USA; NFL: Overall view of CenturyLink Field during the second half of a game between the Seattle Seahawks and the Tennessee Titans. Seattle defeated Tennessee, 27-17. Mandatory Credit: Joe Nicholson-US PRESSWIRE
Often in the world of sports we are told the same clichés and platitudes over and over again as if they are irrefutable fact even when there is little or no evidence to support them. Narratives tend to snowball out of control to the point where commentators and so-called experts will spew statements based on minute sample sizes or wildly speculate about non-existent trends based on the last thing they’ve seen. People find these narratives engaging, and while some are accurate, others are not even close to being correct. With this in mind I decided to tackle the issue of home-field advantage and the Seahawks legendary 12th man. Seahawks fans know that their team was virtually unbeatable at home during the glory years of the early-mid 2000’s including 8-0 home records in 2003 and 2005 but what about today? Football experts talk about CenturyLink Field as if it is an absolute fortress but is this actually the case? The many false starts, the sheer noise and the unforgettable “Beast Quake” paint the picture of the Seahawks as a dominant home team but how strong is the 12th man really? I did a little bit of research to discover how strong Seattle’s home field advantage has been over the last couple of years in the context of the NFL as a whole.
The sample I used for my data was the last two years, which also coincides with the Pete Carroll era in Seattle. I thought this was an appropriate sample because in comparing home and roads performances there would be a full season’s worth of each for every NFL team. That seemed to be a valid sample to analyze and also one that would be easy to conceptualize. If I said that the Arizona Cardinals were 10-6 at home over the last 2 years you would have an idea of how well they played because you can imagine how good a 10-6 team is. Additionally, I thought given the widespread changes that Carroll has introduced to the Seahawks, both in terms of scheme and personnel, any seasons before he took over would no longer be helpful in projecting of the kind of home field advantage the Seahawks can expect in 2012.
My first step was comparing home and road records. This gives the simplest account of how teams fare at home compared to on the road. Saying that the New England Patriots have the best home field advantage in the league because they have the best home record is failing to see the entire story. The New England Patriots have been a dominant team over the last two years both home and away, their home field does not actually make them perform that much better. This chart shows the teams that win the most games at home compared to how many they win away. You may notice that there are a couple of games missing leading some teams to be have a decimal point in the difference between their home and away records. This is due to the fact I couldn’t bring myself to count games taking place in London as home games for the “home” teams, so there are two games omitted from this chart.
Team |
Home Record
Away Record
Difference
AZ
10-6
3-13
7
BAL
15-1
9-7
6
GB
15-1
10-6
5
JAX
9-7
4-12
5
SF
11-4
7-9
4.5
BUF
7-9
3-13
4
IND
8-8
4-12
4
SEA
9-7
5-11
4
ATL
13-3
10-6
3
CLE
6-10
3-13
3
NE
15-1
12-4
3
NYJ
11-5
8-8
3
STL
6-10
3-13
3
SD
10-6
7-9
3
KC
10-6
7-9
3
CAR
5-11
3-13
2
DET
9-7
7-9
2
HOU
9-7
7-9
2
NO
13-3
11-5
2
CHI
10-6
9-7
1
CIN
7-9
6-10
1
MIN
5-11
4-12
1
NYG
10-6
9-7
1
TEN
8-8
7-9
1
TB
7-8
7-9
0.5
DAL
7-9
7-9
0
PIT
12-4
12-4
0
DEN
6-10
6-10
0
OAK
8-8
8-8
0
MIA
5-11
8-8
-3
WAS
4-12
7-9
-3
PHI
7-9
11-5
-4
As you can see Seattle has won 4 more games at home over the last two years than they have won away. This places them in a tie for 6th place in the league over that time span. The average NFL team won 2 more games at home in the 2009-2010 period than they did away, or 1 per year, and the Seahawks double that total. This bodes fairly well for the theory of the powerful 12th man, although it should be noted that division rivals Arizona (leading the league with a whopping 7 games better at home) and San Francisco (one of the beneficiaries of the awkward decimal point at 4.5 games better) show more extreme home/away splits in their records than do the Seahawks.
The second chart I built measures the home/away splits of all 32 NFL teams in terms of point differential. Point differential can be more descriptive as to how teams played as well as more predictive of future results. We see again that teams that are the most dramatically better at home aren’t necessarily great teams that dominate at home but usually teams that are average to good at home and struggle on the road. Keep in mind that all the numbers on the below chart are in per game terms.
| Team | Home Point Differential | Away Point Differential | Difference |
| SF | +11.2 | -2.3 | 13.5 |
| AZ | +2.1 | -11.2 | 13.3 |
| SD | +11.0 | -1.6 | 12.6 |
| GB | +16.9 | +4.8 | 12.1 |
| DET | +8.7 | -1.8 | 10.5 |
| NYJ | +6.9 | -2.1 | 9 |
| BUF | -2.1 | -10.6 | 8.5 |
| NO | +13.1 | +4.7 | 8.4 |
| IND | -0.2 | -8.5 | 8.3 |
| PIT | +12.2 | +3.9 | 8.3 |
| STL | -3.9 | -11.9 | 8 |
| SEA | +0.8 | -6.5 | 7.3 |
| BAL | +9.7 | +2.7 | 7 |
| MIN | -3.2 | -8.7 | 5.5 |
| DAL | +2 | -3.2 | 5.2 |
| ATL | +8.9 | +4.1 | 4.8 |
| JAX | -2.5 | -6.9 | 4.4 |
| KC | +0.7 | -3.6 | 4.3 |
| CAR | -6.7 | -9.6 | 2.9 |
| NYG | +2.5 | 0 | 2.5 |
| NE | +13 | +10.6 | 2.4 |
| WAS | -4.2 | -6.5 | 2.3 |
| HOU | +3.1 | +1.4 | 1.7 |
| TEN | +1.6 | +0.6 | 1 |
| DEN | -5.6 | -6.4 | 0.8 |
| CIN | -1.6 | -2.3 | 0.7 |
| CHI | +1.6 | +1.1 | 0.5 |
| OAK | -0.9 | -1.3 | 0.4 |
| CLE | -4.7 | -4.7 | 0 |
| TB | -6.3 | -5.6 | -0.7 |
| MIA | -2.4 | -0.7 | -1.7 |
| PHI | +3 | +5.5 | -2.5 |
By this measure the Seahawks rank 12th in terms of home field advantage. They have been very average at home outscoring their opponents by 0.8 points per game and they have played fairly poorly on the road being outscored by 6.5 points per game. The typical NFL team has had a point differential that is 5.075 points per game better at home than on the road and the Seahawks eclipse this mark by a significant percentage by being 7.3 points per game better at home. The Seahawks play far better at home and their superiority at home is still apparent when put in the context of the entire NFL.
When I began digging up these numbers I didn’t know exactly what I was going to find. On one hand I have seen the Seahawks play enough to know that they are clearly a better team at home. On the other hand being better at home is not altogether surprising, and I expected that almost all teams would enjoy significant home field advantage. Without knowing how much better at home an NFL team can be expected to be, knowing that the Seahawks were better in their own stadium didn’t mean very much at all. As it turns out over the last two years the Seahawks have enjoyed some of the best home field advantage in the league in two different measures. It is nice to know that the 12th man is doing its/their (don’t know the appropriate pronoun to put there) job and that playing in Seattle does indeed give our beloved Seahawks a boost. With an improved roster in 2012 hopefully this can be the year the Seahawks can take the step from much better at home to dominant at home.