Is there such a thing as dome-field advantage in the NFL?
In 2020, the Las Vegas Raiders relocated to a new domed venue, Allegiant Stadium, in their first season in Paradise, Nevada. The Los Angeles Rams and Los Angeles Chargers made a similar transition, as they began to play home games inside the newly constructed, fully enclosed SoFi Stadium.
How did these franchises fare during the 2020 season? The Chargers endured a 7-9 season but went 4-4 at home, the Raiders went 8-8 and won just two of eight games at home, and the Rams made the playoffs and won six of eight games at home.
These aerial shots of @SoFiStadium are unreal.— Rams Brothers (@RamsBrothers) June 24, 2020
(📸: @westcoastaerial) pic.twitter.com/4eOV0jYoA2
All three completed at least half of their games under a roof, as opposed to out in the open climate, but experienced vastly different results.
Nonetheless, some NFL fans have long argued that playing inside a dome stadium provides a distinct advantage.
That may be the case, but not in the way you might think.
Let's explore the concept of dome-field advantage and determine which teams or players benefit most from competing inside an enclosed stadium.
Win percentage of teams with dome stadiums vs. open stadiums
In 1968, the Houston Oilers (now the Tennessee Titans) became the first NFL franchise to host its home games inside a domed building. That year, the Oilers finished 7-7 and lost their first four games at home.
The following season, Houston finished 6-6-2, then hit a four-year period of decline, with, at best, a four-win season in 1971, and, at worst, a pair of 1-13 records in 1972 and 1973.
It's safe to say dome-field advantage did not exist for the Oilers in the early 70s, but what about the other teams who eventually built domed stadiums?
In 2013, an NFL fan shared this statistical research on Reddit, in which he analyzed the difference in win percentage for teams that played home games inside open-roof stadiums, compared to teams that played home games under a retractable roof or dome.
Three NFL teams have never won a primetime game played in a dome/retractable roof stadium. The Bengals (0-7), Jaguars (0-4), and Dolphins (0-3). https://t.co/A0oFcVR7jr— NFL on Reddit (@NFLonReddit) May 24, 2018
At the time of his research, the franchises that, at one point, used an enclosed stadium for home games were the Oilers, Rams, Atlanta Falcons, Arizona Cardinals, Dallas Cowboys, Detroit Lions, Indianapolis Colts, Minnesota Vikings, New Orleans Saints, and Seattle Seahawks.
His statistical analysis concluded that outside teams at home owned a .583 win percentage, while dome/retractable-roof teams boasted a .545 win percentage.
The data displayed minimal discrepancy, but on the road, the difference was more apparent.
Outside teams won 43.3% of their away games, whereas dome/retractable-roof teams won 38.8% on the road.
In the postseason, outdoor teams won 67.5% of home games, compared to 66.7% for dome/retractable teams, and in playoff road games, outdoor teams won 38.2% of the time. Dome/retractable teams won just 24.4% of those matchups.
If anything, playing home games inside a dome created a disadvantage, as teams accustomed to that environment did not adjust well when they visited outdoor sites.
The teams used to an open, outdoor stadium, where changes in climate are typically frequent, seemed to perform better on the road, when they had to adjust to a new stadium and other unfamiliar elements.
What does the Super Bowl say about dome vs. open stadiums?
Since 2010, the Saints are the only franchise with a home, domed stadium that went on to win a Super Bowl. They secured that title inside the open Hard Rock Stadium in Miami and defeated the Colts, whose home games were inside a retractable-roof stadium.
On this date in 2010...the Saints beat the Colts in Super Bowl XLIV.— ESPN Stats & Info (@ESPNStatsInfo) February 7, 2020
New Orleans sealed their first Super Bowl after CB Tracy Porter stepped in front of Reggie Wayne, picked Peyton Manning’s pass & returned it 74 yds for a TD to give the Saints a 31-17 lead with 3:12 remaining. pic.twitter.com/r2Je5fc5E6
Since New Orleans' championship in 2010, only one dome team, the Atlanta Falcons, has reached the Super Bowl. That team lost to an open-field opponent, the New England Patriots, in one of the largest come-from-behind victories in Super Bowl history.
How does player performance change inside a dome?
While dome teams have struggled in the postseason, particularly on the road, closed-roof venues appear to serve players in an interesting way.
Looking at quarterbacks whose home stadiums were domes, most saw a noticeable increase in passing production on an enclosed field.
Matthew Stafford — who called Ford Field home for 12 seasons — completed 63.46% of his passes inside a dome and 63.11% under a retractable roof. When he competed at an open stadium, his completion percentage dipped to 61.08%. His quarterback rating also went from 91.3 in a dome to 87.4 outside.
Drew Brees, the all-time leader in passes completed (7,142) and single-season leader in completion percentage (74.4%), also seemed to benefit from playing games inside a dome.
Brees' completion percentage was 69.76% in that setting, but 65.33% when throwing passes in an outside stadium.
Drew Brees, who spent 15 years with the Saints and led them to a Super Bowl championship in 2010, walks away with 80,358 yards passing over his career, the most in #NFL history. https://t.co/4V2dy17Xky pic.twitter.com/wwBSU0vrGx— USA TODAY Sports (@usatodaysports) March 14, 2021
You can find a similar statistical pattern with Vikings quarterback Kirk Cousins and Falcons gunslinger Matt Ryan.
What advantage does playing in a dome offer?
Although these quarterbacks were more accurate under a closed roof, their teams did not necessarily see an uptick in overall performance or a boost in the win column.
The reason may be that other quarterbacks who played home games in open venues also improved statistically when visiting a dome.
Tom Brady has spent his 22-year career with the New England Patriots and Tampa Bay Buccaneers (both outdoor-stadium franchises), but his completion percentage inside a dome is nearly five percentage points higher, compared to outside (68.59% vs. 63.66%). His passer rating is also 111.8 in a dome and 96.4 outdoors.
The same goes for Aaron Rodgers (67.03% in a dome vs. 64.6% outside, 108.4 rating in dome vs. 102.8 rating outside) and Ben Roethlisberger (69.75% vs. 63.55%, 105 rating in dome vs. 93.1 outside).
So what can you count on to be true when two teams meet in an enclosed stadium?
A study conducted on games from 2003 to 2015 found that total points per game scored in outdoor venues was 42.4, while games played in a dome or retractable-roof stadium combined for 46.2 points per contest.
An indoor stadium may not lend an advantage to any one team, but it can help predict whether a matchup will be high-scoring.
Thus, the edge here goes to the sports bettor looking to make an Over/Under wager more than any one team or player.
In the future, more franchises may opt to break ground on domed and retractable-roof venues, but the data indicates it isn't in their best interest, unless every team is on an equal playing field. Until then, the teams with open-field stadiums appear best suited to march on to victory, especially when the games count the most.