Home Field Advantage Explained...

Sort Of

Scorecasting: The Hidden Influences Behind How Sports Are Played and Games Are Won was released at about the same time my book The Fix Is In was. Now I'm willing to make a leap of faith and say that I'd guess at least one of the two authors is smarter than I am. I know both make more money than I do. One, Tobias J. Moskowitz, is the Fama Family Professor of Finance at the University of Chicago. The other, L. Jon Wertheim, is a senior writer for Sports Illustrated.

That said, in reading their tome--from which I will liberally quote from below--I believe they missed something. Either that, or the two of them are too chicken to say what they really meant (but I'm not).

The pair devote two chapters to the topic of home field advantage. They ask, "What causes this phenomenon? Does it even exist?"


Clearly it does. According to the authors' research, in the last ten years the percentage of home games won in the MLB was 53.9%, in the NHL 55.7%, in the NBA 60.5%, and in the NFL 57.3%.

Before the authors get into the nuts and bolts behind why this is the case, they write the following on pages 115-116:

“Before considering the causes of the home field advantage, keep this premise in mind: There is considerable economic incentive for home teams to win as often as possible. When the home team wins, the consumers—that is, the ticket-buying fans—leave happy. The better the home team plays, the more likely fans are to buy tickets and hats and T-shirts, renew their luxury suite leases, and drink beer, overpriced and watered down as it might be. The better the home team plays, the more likely businesses and corporations are to buy sponsorships and the more likely local television networks are to bid for rights fees. A lot of sports marketing, after all, is driven by the desire to associate with a winner. In San Antonio, if the fans consistently left disappointed, it’s unlikely that AT&T would slather its name and logo on most of the surface area of the arena or that Budweiser Select, Sprite, “your Texas Ford dealers,” Southwest Airlines, and other sponsors would underwrite T-shirt giveaways, Bobble Head Night, and a halftime shooting contest."

“By extension, the leagues have an incentive for the home teams to win. Although attendance and revenue rise in step with winning percentage for most teams, they rise even more sharply with home winning percentage. And healthier individual franchises make for a stronger collective. Does this mean leagues and executives are fixing games in favor of home teams? Of course not. But does it make sense that they would want to take subtle measures to endow the home team with (legal) edges? Sure. It would be irrational if they didn’t.”

From this point, the authors eliminate causes of home field advantage. It's not the crowd, they determine. It's not the field/arena/stadium itself. It's not weather conditions. And it's not the rigors of travel from city to city.


They do make a case, in the realm of the NBA and NHL, that scheduling plays a role. Often times, teams in these leagues make road trips in which several games are crammed into a short time frame, basically wearing teams out. When road teams play back-to-back contests on consecutive nights, they lose much more often than they win (take note, gamblers).

In fact, they quote one anonymous NBA owner as saying, "If only [fans] knew how the NBA scheduled games. Teams submit blocked dates for their arena [i.e., dates when the circus is using the building or the NHL team is using the facility]. The NBA picks ‘marquee TV match-ups,’ and then one guy figures out the rest with marginal help from software. Teams kiss his ass because we know he can throw more losses at us than Kobe can!”

So if it isn't any of those factors, what causes a home team to win more often than it should?


As the authors write on page 138, "What we’ve found is that officials are biased, confirming years of fans’ conspiracy theories. But they’re biased not against the louts screaming unprintable epithets at them. They’re biased for them, and the bigger the crowd, the worse the bias. In fact, “officials’ bias” is the most significant contributor to home field advantage. “Home cooking,” as it’s called, is very much on the menu at sporting events.”

The authors then go through each major league sport and show where they found--and could prove--these officials' biases existed.

For Major League Baseball, they write, "In baseball, it turns out that the most significant difference between home and away teams is that home teams strike out less and walk more—a lot more—per plate appearance than do away teams....For the most ambiguous pitches—the ones on the corners—the home-away called-strike discrepancy is largest, which makes sense....Over the course of a season, all of this adds up to 516 more strikeouts called on away teams and 195 more walks awarded to home teams than there otherwise should be, thanks to the home plate umpire’s bias. And this includes only terminal pitches—where the next called pitch will result in either a strikeout or a walk. Errant calls given earlier in the pitch count could confer an even greater advantage for the home team....Taking the value of a walk and a strikeout in various game situations, this adds up to an extra 7.3 runs per season given to each home team by the plate umpire alone. That might not sound significant but cumulatively, home teams outscore their visitors by only 10.5 runs in a season. Thus, more than two-thirds of the home field advantage in MLB comes by virtue of the home plate umpire’s bad calls." (pages 141-149)

In the National Football League, they write, "Home teams receive fewer penalties per game than away teams—about half a penalty less per game—and are charged with fewer yards per penalty….It turns out that more valuable penalties, those that result in first downs, also favor the home team....Before instant replay, home teams enjoyed more than an 8 percent edge in turnovers, losing the ball far less often that road teams. When instant replay came along to challenge wrong calls, the turnover advantage was cut in half [With the introduction of the instant rule, home field advantage shrunk by 29.4 percent according to the authors]."

They continue: "It turns out that away teams are indeed more successful in overturning a call than home teams are, but only modestly so (37 percent versus 35 percent). Both are slightly more successful than official challenges (33 percent), which are challenges initiated by an official in the last two minutes of each half on close plays. These statistics are misleading, though, because as we saw in baseball and soccer, referees are less likely to make biased judgments when the game is no longer in doubt. So what happens if the home team is behind? When the home team is losing, a challenge made by the home team is successful 28.4 percent of the time. But a challenge made by the away team is successful 40 percent of the time. Thus, away teams seem to be getting more that their fair share of bad calls when they are winning, which is when bad calls would be most valuable to the home team."

"Could referee bias explain a large part of the home field advantage in football? Absolutely….The fact that home teams in football have better offensive stats—such as rushing more successfully and having longer time of possession—could be the result of getting more favorable calls, fewer penalties, and fewer turnovers." (pages 150-152)

With the National Basketball Association, they detailed the following: "Home teams shoot more free throws than away teams—between 1 and 1.5 more per game. Why? Because away teams are called for more fouls, particularly shooting fouls. Away teams also are called for more turnovers and more violations."

 Also, It turns out that offensive and loose ball fouls go the home team’s way at twice the rate of other personal fouls. We can also look at fouls that are more valuable, such as those that cause a change of possession. These fouls are almost four times more likely to go the home team’s way than fouls that don’t cause a change of possessionThe chance of a visiting player getting called for traveling is 15 percent higher than it is for a home team player."

"Referee bias could well be the main reason for home court advantage in basketball. And if the refs call turnovers and fouls in the home team’s favor, we can assume they make other biased calls in favor of the home team that we cannot see or measure." (pages 152-155)


The same seems to go in the National Hockey League as well, "Home teams in hockey get 20 percent fewer penalties called on them and receive fewer minutes in the box per penalty….The net result is that on average per game, home teams get two and a half more minutes of power play opportunities…than away teams.” By the authors' math, this equates to a 0.25 goal advantage per game in favor of the home team, that is 80 percent of the 0.30 average goal differential between home and away teams seen during the course of a season.

So if the referees are to blame for all of this, what's the cause of their behavior?

Before they answered that question, they decided to add a caveat on page 157: "First, let’s be clear: Is there a conspiracy afoot in which officials are somehow instructed to rule in favor of the home team, especially since the league has an economic incentive to boost home team wins? Almost unquestionably no. We’re convinced that the vast majority of, if not all, officials are upstanding professionals, uncorrupted and incorruptible, consciously doing their best to ensure fairness. All things considered, they do a remarkable job."

"Almost unquestionably no?" That's not as strong of a statement as it appears to be. Isn't that a way of saying "we doubt it, but we're not ruling it completely out?" But I digress...

What's the cause then of the official-caused home field advantage? Psychology. The referees are unconsciously motivated to conform to the wishes of the home crowd. On top of that, the authors make the case that the greater number of fans in attendence, the more biased the refs become in their favor, wanting to be subconsciously be a part of that group, because "referees are, finally, human."

Amazingly, the authors fail to believe that though human, referees could be corrupted. In fact, as shown above, they actually write that they are "incorruptible." For my money, any credibility these two authors had went out the window with that absurd claim. Maybe if I show them the numerous FBI files I have of corrupted officials they'd change their mind.

But the authors do add one final note of interest. On page 160 they write: "Remember, too, that on top of the anxiety caused by passionate and sometimes angry fans, the refs receive stress from their supervisors and superiors. In a variety of ways—some subtle, some not—officials must take in cues that the league has an economic incentive for home teams to do well. If your boss sent a subtle but unmistakable message that Outcome A was preferable to Outcome B, when you were forced to make a difficult, uncertain, and quick decision, how would you be inclined to act?" 

Is that a way of saying that officials are actually motivated to make these "homer" calls by the leagues that employ them? That games are manipulated by officials to the whims and wants of owners? Perhaps. Yet it is not a strong enough stand to make despite this seed of doubt.

But it's a start.