In 2019, the away team won every game in the World Series. This led to speculation as to how that could happen. Teams are supposed to have an advantage when they have home field. If you look at history, there is plenty of evidence to back this up. The question is, “what causes it?”
The Crowd
Sports fans often believe that having fans in the stands cheering raises the level of the home team’s play. While this may impact some players, the data from studies shows that players aren’t rattled by booing during an away game, and some players are motivated by it. If you look at free throws in NBA basketball games over the 2018-2019 season, the data shows that there is no change in players’ free throw numbers based on where they play. The crowd doesn’t seem to have an effect on how well the players play.
The Referees
Another theory is that there is bias from referees that favors the home team. If you examine basketball, you can see that over the season in 2018-2019, the home team received 0.8 more free throws from penalties on average. The overall advantage was 2.7 points for the home team, so this number accounted for 22% of the home advantage. These numbers appear to hold in other sports, including soccer, baseball, and hockey.
Travel
Travel quite likely has an impact on home advantage. Players spend more time in their home venue, and they can experience jet lag when they travel. Studies have shown that traveling to a different state followed by back-to-back games is related to a reduction in player performance.
The Decline of Home Field Advantage
Although there is still a home field advantage that exists in many games, studies show that it is declining. There have been changes in how games are officiated that can eliminate bias. Technology has allowed instant replays in slow motion in different sports, and advances in medicine allow trainers to adopt training programs that help players play at their best. Although there is still a home advantage, it appears to be on the decline.