NBA Home Court Advantage: Why It Exists but Isn't as Important as You Think

Adam Fromal@fromal09National NBA Featured ColumnistNovember 11, 2011

DALLAS, TX - JUNE 16: Owner Mark Cuban of the Dallas Mavericks during the Dallas Mavericks Victory celebration on June 16, 2011 in Dallas, Texas. (Photo by Brandon Wade/Getty Images)
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In the NBA, playing at home just seems to have a magical effect.

There's a reason that teams strive not just to make the playoffs, but also to finish with a good enough record to earn home court advantage throughout the postseason. After all, teams can't possibly lose when they're playing in front of thousands of their own rowdy fans, all screaming their heads off in order to intimidate the opposition and cheer their own team to victory.

In almost any given season in NBA history, home teams have won roughly 60 percent of games played. As a result, it is absolutely impossible for me to deny the existence of home court advantage. But I can question why it exists, and more importantly, how much it actually matters.

After all, even David Blaine had tricks up his sleeve that he secretly used to seem magical. The NBA, in much the same way, has hidden explanations to the voodoo magic of the home court.  

They say a good magician never reveals his tricks, but fortunately magic is only a metaphor here. Let's take a look at why home court actually exists.  

Random Arena Advantages

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BOSTON - JUNE 10:  A detail of a screw holding together the parquet floor during Game Four of the 2010 NBA Finals between the Los Angeles Lakers and the Boston Celtics on June 10, 2010 at TD Garden in Boston, Massachusetts. NOTE TO USER: User expressly ac
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Much like the famed "Smurf Turf" at Boise State University, many NBA courts, and cities for that matter, possess unique characteristics that give the home team inherent advantages, simply because they're already used to playing there.

While not as drastic as the random nooks and crannies at baseball stadiums, each and every basketball city has its own quirks that home players can exploit. 

Take for example the Boston Garden. Even if you don't believe that Red Auerbach used to only let opposing teams have cold water in addition to playing random tricks on them with the intent of breaking their concentration, you can't deny that the parquet floor plays right into the hands of the Boston Celtics.

There aren't as many dead spots as there were back in the days of Bill Russell, John Havlicek, Bob Cousy and the C's of old, but the floor is still tricky to navigate. Plus, the pattern of the floor can throw off a player's visuals if he isn't used to it.

What about the altitude that the Denver Nuggets play at? The other 29 teams in the NBA are accustomed to playing at drastically lower levels, thus making each and every game at the Pepsi Center a little bit more of a struggle.

The last examples I'll bring up are specific cities like New Orleans and New York. There is no chance you'll be able to convince me that the young men playing in the NBA aren't at least slightly affected by the temptations that are so ever-present on Bourbon Street and in The City That Never Sleeps.   

A Little Bit More Rest

ATLANTA, GA - MAY 12:  Josh Smith #5 of the Atlanta Hawks against the Chicago Bulls in Game Six of the Eastern Conference Semifinals in the 2011 NBA Playoffs at Phillips Arena on May 12, 2011 in Atlanta, Georgia.  NOTE TO USER: User expressly acknowledges
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One of the most overlooked aspects of home court advantage is the fact that the teams playing at home generally have a little bit more rest than their oppositions. Generally, home games come during homestands in which the teams get to spend multiple days in the same city instead of traveling from one city to the other night after night. 

But even if the two teams playing are coming off the same amount of rest, there's still the advantage of having a better quality of rest, even if the quantity is similar. Something tells me that NBA players drastically prefer the comforts of home cooking and their own beds to the squirming discomfort of a foreign hotel. 

The following quote (I apologize for the length, but all of it is both important and relevant to the topic at hand) comes from a Harvard study about the effect of rest on performance in the NBA: 

"The fact that home teams in the NBA win so large a fraction of the time is quite a fascinating observation since it implies that factors other than the skill of the competing teams play critical roles in the outcome of games in professional basketball. We have examined one of these factors, the travel factor, from two points of view, namely the effect of the fact that, on balance, the traveling team has a schedule which provides fewer days of rests between games, and that just being on the road an extended number of days could lead to a decrease in athletic performance. Our analysis of the 2,415 games which took place in the 2004-2005 and 2005-2006 seasons of the NBA indicates that the travel schedule does seem to be a real, although not dramatic factor contributing to the NBA’s home team advantage. On average, for these two seasons, the home teams scored 3.24 more points than the visitors, of which 0.31 points arise from the smaller amount of rest that the NBA schedule provides the traveling team and 2.93 points are associated with other, non-related factors. The travel schedule effect is most clearly illustrated by the fact that visiting teams with back to back games are estimated to be 1.77 points worse off on average than visiting teams that are fully rested. The data also suggest that traveling teams score one point less during their second game on each trip, but this observation is only weakly significant. 

When the issue of the home team advantage was studied with respect to the number of games won or lost, as opposed to the number of points scored, the data once again showed the importance of the tight schedule faced by the traveling teams. As with the margin of victory measured in points, the condition indicating the highest effect was when the visiting team played the second of a back to back pair of games. In this case, the odds of the visiting team winning were decreased to an estimated 75% of those corresponding to the fully rested state, although the level of significance was weak. Based on these analyses, we conclude that the extraordinary high home court advantage enjoyed by NBA teams is partially explained by the tendency of the NBA schedules for the traveling teams to have reduced rest, but that the bulk of the advantage arises from other, non-related factors." 

So now that I've shown how arena effects and rest can both provide advantages to the home team, let's take a look at the biggest factor of all. 

Referee Bias

MIAMI, FL - JUNE 02:  LeBron James #6 of the Miami Heat talks with referee Ken Mauer #41 against the Dallas Mavericks in Game Two of the 2011 NBA Finals at American Airlines Arena on June 2, 2011 in Miami, Florida. NOTE TO USER: User expressly acknowledge
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According to Tobias Moskowitz's book Scorecasting, "Long story short, 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." In order to give credit where it is due, I must tell you know that the following ideas and statistics are all simplified versions of the ones provided in the aforementioned book. 

Both home and away teams shoot 74.6 percent from the free throw line, but the home teams gain an advantage in the supposedly free points category because they shoot between one and one-and-a-half foul shots per game. This already means that home teams have around a 0.8 points per game advantage on their traveling opposition.

As for the types of calls that referees can make, the more objective ones are fairly standard. 24-second shot clock violations and turnovers on five-second violations and inbounds plays are called at the same rate for both teams. But as for the calls where referees have to apply their own judgment, like traveling calls, those are more skewed. In fact, traveling is called 15 percent more often on visiting players than home players.

Now here's where I go back to directly quoting Moskowitz:

"If we give credit to the referees for the more ambiguous turnover differences and computed the value of those turnovers, this would also capture another quarter of the home team's advantage [3.4 points per game]. Attributing some of the other foul differences to the referees and adding the effects of those fouls (other than free throws) on the game, this brings the total to about three-quarters of the home team's advantage. And remember, scheduling in the NBA explained about 21 percent of the home team's success, as well. That adds up to nearly all of the NBA home court advantage."

Home Team Psychology

MIAMI, FL - APRIL 27:  Andre Iguodala #9 of the Philadelphia 76ers walks off the floor during game five of the Eastern Conference Quarterfinals in the 2011 NBA Playoffs against the Miami Heat at American Airlines Arena on April 27, 2011 in Miami, Florida.
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You can be sure that NBA players can tell when they're playing better. After all, the live, sleep, breathe, eat, think and even dream basketball during the season. Well, most players do at least (cough Baron Davis cough). When shots are falling more often, they tend to internalize that.

A writer named David Hess and the rest of his crew at teamrankings.com took a look at NBA splits from 2003 to the present day. He found the following data:

Stat Home Away Difference
Steals 7.39 7.27 0.12
Turnovers 13.59 14.02 -0.43
Offensive Rebounds 11.52 11.07 0.45
Defensive Rebounds 30.75 29.7 1.05
Total Rebounds 42.27 40.77 1.5
Points 99.72 96.41 3.32
Fastbreak Points 11.89 10.47 1.43
Two-point Field Goal Percentage 48.7% 47.2% 1.5%
Three-point Field Goal Percentage 36% 35.5% 0.5%
Free Throw Percentage 75.7% 75.5% 0.2%
Fouls 21.13 22.15 -1.02

As you may have noticed, the only negative differences are in the statistics that home teams want to be negatives: turnovers and fouls. Clearly, players perform better at home. 

But why? Well, in psychology we have a term called the self-fulfilling prophecy. 

Because players hear that they play better at home, they internalize the "prophecy" and then, having convinced themselves that they play better at home, they do indeed play better at home. 

And thus concludes the first part of this article now that it's abundantly clear both that home court advantage exists and why it exists. But since the NBA is all about the playoffs, how much does it actually matter? 

This is where you may be surprised.

Home Court Advantage Among the Elite Teams

CHICAGO, IL - MAY 26:  Derrick Rose #1 of the Chicago Bulls walks towards the bench against the Miami Heat in Game Five of the Eastern Conference Finals during the 2011 NBA Playoffs on May 26, 2011 at the United Center in Chicago, Illinois. NOTE TO USER:
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Like I said at the beginning of this article, it's all about the playoffs in the NBA. I recently finished reading a book called The Franchise by Cameron Stauth, a story that detailed the rise of the 1988-1989 Bad Boy Detroit Pistons to the top of the heap in The Association. I can't even count how many time Jack McCloskey and the other members of the Detroit organization hammered home the fact that they desperately wanted to enjoy home court advantage during the postseason. 

After all, it seems to be fairly common knowledge that the elite teams in the NBA are elite at home. Some people even think that they are elite because they are elite at home. And that's where they're wrong. 

I had a sneaking suspicion that it was on the road, overcoming all the disadvantages that were laid out above, where the best teams in the NBA showed they had what it took to become champions. Yes, the elite teams had gaudy home records, but were they really that gaudy compared to their overall records?

To figure this out, I took a look at the standings and playoff seedings from the 2000-2001 season up until this past season. Breaking down the records of the 16 teams that made the playoffs each year, I recorded their records at home and their overall records, then subtracted their overall winning percentage from their home winning percentage and recorded the difference. 

Each NBA team plays exactly 41 of their 82 regular season games at home each season. So if a team like the 2004-2005 Phoenix Suns goes 31-10 at home and 62-20 overall, that means that they performed exactly the same on the road as they did at home, giving them a "difference" of exactly 0. 

If it holds true that the elite teams are elite because they're better at home, then the top seeds will have the highest differences. But that was not the case at all, as you can see from the following graph. 

While there wasn't a drastic difference between No. 1 seeds and No. 8 seeds, there was a noticeable correlation: the worse the seed, the bigger the difference between home winning percentage and overall winning percentage. 

Since basketball games are always played either at home or on the road, that means that the better seeds actually won a higher percentage of their games on the road than the lower seeds. 

So the next time you think about home court advantage, don't make the mistake of thinking it's the only thing that matters. No matter how good a team is at home, to be truly elite they have to be able to win on the road at a high rate. 

But don't let that dissuade you from attending your favorite team's next home game and screaming your head off. I fully support that, so long as you aren't cheering against my team. 

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