Writers of Pro Football Prospectus 2008

18 Oct 2007

How Much Do Road Crowds Hurt An Offense?

In the Extra Point thread discussing the merits (ahem) of Roger Goodell's master plan to put radios in all players' helmets, Brian asked:

Brian: Do we even have any statistical proof that offensive efficiency drops league-wide when teams are on the road?

Stuart Fraser: We have half the answer already -- in the St. Louis chapter of PFP 2007, Bill and Aaron investigated false start penalties, showing that teams accrued more of them on the road and in domes, and Bill Moore showed the previous year that some stadiums do draw more false starts than others, with the Edward Jones Dome in St. Louis, Lincoln Financial Field in Philadelphia and Buffalo's Ralph Wilson Stadium leading the way.

But what about the plays that aren't blown dead? Are those affected by backs or linemen not hearing assignments clearly, teams having to go to a silent snap count, diminished ability to audible or other problems created by crowd noise?

We can get some idea of how teams are affected by comparing home and road DVOA. There are two possible approaches -- comparing home and road offensive DVOA to see which teams are most affected by the various disadvantages being on the road brings, or comparing home and road defensive DVOA to see which stadia disrupt opposing offenses the most. I chose the latter, looking for the greatest differences between home and road defensive DVOA (these stats are available in the premium database) for all seasons 1996-2006. This gives a total of 342 team-seasons. I didn't look at this year as the sample size is smaller and the opponent adjustments aren't yet at full strength, so it wouldn't be entirely comparing like with like.

Now, crowd noise isn't the only factor in home advantage, and it's difficult to separate any one factor from any of the others, which is something to keep in mind whilst reading the rest of this article. The statistic I'll be using is "home DVOA" - "road DVOA," and as this is defensive DVOA a better number is negative. Therefore, the stronger the home advantage, the more impaired an opposing offense, the more negative the difference between home and road should be.

The mean difference between home and road defensive DVOA, counting every team for every year, is -7.2% -- that is, offenses are an average of just over 7 percent less effective on the road than they are at home. Dome teams (including Dallas, as Texas Stadium's architecture is built in the style of a dome) fare slightly better than league average, with defensive efficiency up by 8.4%.

There is a lot of variation between teams and years -- the standard deviation is 14.6%. Given this, it's hard to say anything with confidence about the individual teams or stadia (for which the sample size is at most 11), but here's the list of top ten mean home advantages, just for fun:

Team Home Advantage
KC -16.52%
MIN -16.42%
ARI -15.70%
MIA -14.98%
IND -13.69%
BAL -11.43%
DET -10.13%
BUF -9.86%
OAK -9.47%
STL -9.42%

Some of these are names we expected -- the Rams and Bills show up as they did for false starts, Arrowhead is famously noisy, and Minnesota, Indianapolis and Detroit also play in noise-enhancing domes. But Arizona? The Cardinals actually have the greatest single-season difference between home and road defensive DVOA, in 2003, when they posted a respectable -4.6% at Sun Devil Stadium and an, um, less respectable 40.8% on the road. It's not just that year, though -- take it away and they'd still edge out the Lions for seventh. I guess all those empty seats must have been really intimidating. The safer conclusion might be that home advantage isn't just about crowd noise, as the weather in Arizona is probably a factor, though Denver is middle-of-the-pack with a more or less league-average -6.2% advantage.

To close our visit to small sample size theatre, I'd like to honor the players and fans of the Houston Texans, who have combined to produce a team that actually manages to defend better (in four of the franchise's five completed seasons) whilst playing on the road.

So, to summarize -- yes, there is a quantifiable drop in offensive efficiency for road teams (or rise in defensive efficiency for the home teams); it's slightly larger in a dome, suggesting crowd noise is at least a factor; and small sample sizes produce wacky results.

Posted by: Stuart Fraser on 18 Oct 2007

12 comments, Last at 20 Oct 2007, 10:32pm by bigmaq


by McGayTrain (not verified) :: Fri, 10/19/2007 - 11:17am

I can attest to Ralph Wilson's effectiveness. At the Jets game a few weeks ago, Pennington was visibly frustrated throughout the game. He couldn't audible, had to waste several timeouts, as well as several false starts.

by Cosmos (not verified) :: Fri, 10/19/2007 - 11:41am

So now that we do have proof lets take a vote to see who thinks this is one of the dumbest things the NFL could do.....

by MJK (not verified) :: Fri, 10/19/2007 - 12:38pm

I imagine some of this, though, has nothing to do with crowd noise, and instead is a function of road offenses having to fly halfway across the country (in some cases) and disrupt their practice schedule. And when a defense is on the road, it is more tired and so forth, so it will have a drop in efficiency greater than is just accounted for by losing its supporting crowd noise.

by citizen jason (not verified) :: Fri, 10/19/2007 - 1:33pm

So I'm guessing this is answered in the book, but what about Qwest Field? I know that every time there's a false start they flash up a stat about numbers of false starts since ... 2004, maybe? .. and Qwest is ahead by double-digts. (Thank you, NYG ...)

by Sundown (not verified) :: Fri, 10/19/2007 - 3:28pm

#3: A long plane flight and missing a few practices makes guys forget the snap count? Not sure I buy that.

And while travel certainly has some effect, this isn't like high school where guys pile off the bus and are playing within a couple hours.

by James G (not verified) :: Fri, 10/19/2007 - 3:40pm

5 - I can buy it. If it makes you tired, you might be less effective. Also, if you're a west coast team playing a 1 PM eastern game (10 AM for your body clock), you might not be completely sharp.

by Diane (not verified) :: Fri, 10/19/2007 - 4:14pm

I assume that the more drives that start closer to the ends of the fields, the more false starts are likely?

I also assume that DVOA (and thus this analysis) takes this into account?

by Temo (not verified) :: Fri, 10/19/2007 - 4:30pm

So do we now adjust DVOA for certain stadia? Although it just occurred to me that you said the SD was 14%, so I guess not.

by mm (not verified) :: Fri, 10/19/2007 - 6:19pm

Part of this also may be measuring the number of close games they play. If a game is a blowout either way, the crowd would likely be less vocal.

by Brian (not verified) :: Fri, 10/19/2007 - 9:32pm

What about penalties in general? One of the strongest theories about home field advantage in all sports is that refs feel subconscious psychological pressure to favor the home team.

by JoshuaPerry (not verified) :: Sat, 10/20/2007 - 11:59am

AGREE lets see some penalty stats. And if you want to increase traffic/sell more books, how about some comparisons to spread vs officiating crew, maybe find an NBA style controversy.

by bigmaq (not verified) :: Sat, 10/20/2007 - 10:32pm

"Bill and Aaron investigated false start penalties, showing that teams accrued more of them on the road and in domes, and Bill Moore showed the previous year that some stadiums do draw more false starts than others, with the Edward Jones Dome in St. Louis, Lincoln Financial Field in Philadelphia and Buffalo’s Ralph Wilson Stadium leading the way."
Could we please have all of the statistics. Living in Seattle I am sick and tired of the Hawks PR Machine hyping all of the false starts and 12th Man garbage. I seem to recall that if one eliminated one Giant player's false starts (8 or 9) from one game from the statistics that the overall false starts by visiting teams at Qwest in '05 were reduced by 50% placing the number slightly under the norm for stadiums.