“Football Freakonomics”: How Advantageous Is Home-Field Advantage? And Why?

The following is a cross-post from NFL.com, where we’ve recently launched a Football Freakonomics Project.

Do home teams really have an advantage?

Absolutely. In their book Scorecasting, Toby Moscowitz and Jon Wertheim helpfully compile the percentage of home games won by teams in all the major sports. Some data sets go back further than others (MLB figures are since 1903; NFL figures are “only” from 1966, and MLS since 2002), but they are all large enough to be conclusive:

League Home Games Won
MLB 53.9%
NHL 55.7%
NFL 57.3%
NBA 60.5%
MLS 69.1%

So it’s hard to argue against the home-field advantage. In fact my Freakonomics co-author Steve Levitt once wrote an academic paper about the wisdom of betting (shh!) on home underdogs (more here).

But why does that advantage exist? There are a lot of theories to consider, including:

  • “Sleeping in your own bed” and “eating home cooking”
  • Better familiarity with the home field/court
  • Crowd support

Those all make sense, don’t they? In Scorecasting, Moscowitz and Wertheim compile data to test a variety of popular theories. You might be surprised (and maybe even disappointed) to read their conclusion:

When athletes are at home, they don’t seem to hit or pitch better in baseball … or pass better in football. The crowd doesn’t appear to be helping the home team or harming the visitors. We checked “the vicissitudes of travel” off the list. And although scheduling bias against the road team explains some of the home-field advantage, particularly in college sports, it’s irrelevant in many sports.

So if these popular explanations don’t have much explanatory power for home-field advantage, what does?

In a word: the refs. Moscowitz and Wertheim found that home teams essentially get slightly preferential treatment from the officials, whether it’s a called third strike in baseball or, in soccer, a foul that results in a penalty kick. (It’s worth noting that a soccer referee has more latitude to influence a game’s outcome than officials in other sports, which helps explain why the home-field advantage is greater in soccer, around the world, than in any other pro sport.)

 Moscowitz and Wertheim also make clear, however, an important nuance: official bias is quite likely involuntary.

 What does this mean? It means that officials don’t consciously decide to give the home team an advantage — but rather, being social creatures (and human beings) like the rest of us, they assimilate the emotion of the home crowd and, once in a while, make a call that makes a whole lot of close-by, noisy people very happy.

One of the most compelling (and cleverest) arguments in favor of this theory comes from a research paper by Thomas Dohmen about home-field advantage in Germany’s Bundesliga, the country’s top soccer league.

Dohmen found that home-field advantage was smaller in stadiums that happened to have a running track surrounding the soccer pitch, and larger in stadiums without a track.

Why?

Apparently, when the crowd sits closer to the field, the officials are more susceptible to getting caught up in the home-crowd emotion. Or, as Dohmen puts it:

The social atmosphere in the stadium leads referees into favoritism although being impartial is optimal for them to maximize their re-appointment probability.

So it looks like crowd support does matter – but not in the way you might have thought. Keep this in mind next time you’re shouting your brains out at a football game. Just make sure you know who you’re supposed to be shouting at.

 

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  1. Ryan says:

    In the playoffs the advantage is stronger. I looked at games where the road team and the home team have the same regular season record and see how often the home team wins- if it is more than 50% than the home field offered an “advantage.”
    Since 2002, this has happened 12 times and the home team has won 9 of these games.

    You can also look at games where the road team has a better regular season record than the home team- if the home team wins more than the road teams than we can say there is a home field advantage.
    Since 2002, this has happened 5 times and the home team has won 3 of those games

    http://twoandahater.blogspot.com/2010/01/home-field-advantage-in-nfl-playoff_14.html

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    • MW says:

      These results aren’t statistically significant. (This is unsurprising, given the small sample sizes.) For the 9 of 12 result: if the odds of either team winning were equal, then the chance of the home team winning all 12 games is 1/4096, winning 11 is 12/4096, 10 and 9 are 66 and 220/4096 for a total of 299/4096 or about 7.3%. Statisticians don’t get even mildly excited until you’re below 5%. (And you’re not allowed to claim the Higgs particle until one in a million.)
      (I’ve used a one sided test here, as we have a prior expectation that if there is any advantage it goes to the home side. If we were testing whether *some* bias exists, but are agnostic on whether the home or away side is advantaged, we’d have only a 14.6% result.)
      So, assuming we take this bias as undesirable, how can we change it? We could try to insulate the ref from the crowd with noise cancelling headphones. If the game allows each team a limited number of video appeals against ref decisions, we could give more appeals to the visiting team.

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  2. Michael Senchuk says:

    I always presumed that the advantage for hockey was because of putting out the last line, and putting stick down last in face-offs, and in baseball because you had last bat, but that would mean those two would’ve had the biggest advantage. Interesting statistics relevation about officiating.

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    • Mike B says:

      As someone who supports the real advantage baseball provides I would also support changing NFL rules to eliminate the coin toss and basically allow the home team pick of ball or side at the start of the game and in OT. Same for soccer.

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  3. Doug says:

    One thing that seems to tilt the table a bit towards the home team in football is the crowd noise on the important downs making the audible calls inaudible. This would manifest itself in more sacks and/or procedure calls in those circumstances. Does the data show any such effects.

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    • Matt says:

      Agreed. Per the picture above, Seattle prides itself in being the place with the most away-team false start and delay of game penalties. Perhaps this is reflected in the “referee” section above, but I think it’s less of the crowd affecting referees and more of the crowd affecting opponents.

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  4. IE says:

    I think home field advantage in NHL and especially in MLS is even greater than home win advantage percentages show. In hockey and soccer a win is one possible outcome out of three; in other 3 sports there are only 2 possible outcomes (ties in NFL are extremely rare).
    So in case of MLS, the distribution of outcomes would be something like this: 69% / 15% / 16% (W/T/L). That’s obviously a greater skew than 69% / 31% in a two-outcome sport.

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  5. js says:

    what about jersey colors and statistical variations?

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  6. Pete says:

    No Home Field Advantage in Cleveland

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  7. Suman Eldrich says:

    Hidden due to low comment rating. Click here to see.

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  8. RGJ says:

    The post above factoring in regular season records in the NFL leans on a very weak piece of data, IMO. Look at how little early performance indicated the teams standing at the ned of the year….the 6-2 Giants are now 7-7, the Eagles were 1-4 and now on a tear, etc, etc. The wins and losses of of team in September/Oct have little to do with the quality of the team fielded in the playoffs, and certainly, factored times two, the predicability of the matchup.

    I have heard that NFL home field advantage is pretty solidly fixed at three points in the betting world….who make their money at trying to be fair. Anyone study that?

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    • Derek says:

      Ummm, betting lines make their money by taking the most money from both sides. Fair is the OPPOSITE of what bookies try to do.

      I’d be more than happy to set lines & take your bets….

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