But what causes the home field advantage? While my focus is on the NBA, these arguments can apply to other sports, including baseball. What really causes home field advantage – and why it’s on the decline
The crowd has nothing to do with it
Many sports fans believe that crowd noise has a direct impact on player performance.
I analyzed both home and away free-throw shooting of all the players for the NBA’s 2018-19 season. Free throws provide a controlled setting that isolates the home crowd as the only externality potentially affecting the shot.
The results indicated there is no evidence that players perform differently on free throws whether they’re at home or playing away.
Referee bias and traveling
While the crowd appears to have no or very little effect on players’ performance, that might not be the case for the referees.
Several compelling data points support the hypothesis that a large portion of the home edge is due to officiating bias in favor of the home team in the form of subjective calls.
The same holds true for other sports. In soccer, referees add more stoppage time when the home team trails by a goal compared with when the home team is ahead by a goal.
In the NHL, referees call 20% fewer penalties for home teams, which is equivalent to about 0.25 goals.
Another plausible hypothesis for explaining home field advantage – one supported by several studies – involves travel.
Some teams also seem to benefit by playing in regions that have unique weather patterns or altitudes. For example, Denver’s basketball team has the most pronounced home field advantage in all of professional sports.
A declining advantage?
Of course, these aren’t the only possible reasons for the presence of home field advantage.
The question remains open, but researchers do know that the home field edge has been slowly declining over the years
After the NFL introduced instant-replay review of close plays, the home team’s winning percentage dropped from 58.5% to 56%. This may indicate that prior to the adoption of instant-replay reviews, officials awarded more close calls to the home team.
While home field advantage still matters, it’s mattering less and less with every season – just ask the Houston Astros.