Home-field advantage is one of the most well-known ideas in sports, and one of the most misunderstood. In Scorecasting, Professor Tobias J. Moskowitz and L. Jon Wertheim compiled statistics on the probability of teams winning when they play at home. The results are striking.
Soccer has the largest average home advantage across leagues—ranging from a low of 60% winning rates in Asia/Africa to a high of 69.1% in US Major League Soccer.
In basketball, NBA teams win 62.7% of their home games.
International cricket teams win 60.1% of home games. In the NHL, 59% of games are won by home teams. In rugby, the win rate for home teams is 58%, while in American football, it’s 57.6%.
In the United States, Major League Baseball home teams win 54.1% of the time. In Japan’s Nippon League, that’s 53.3%.
So why do home teams win so frequently?
Crowds influence players—FICTION
Some observers cite the noise made by home fans in explaining home-team advantage. That seems particularly the case in stadiums such as Century Link Field, home of the Seattle Seahawks. There, on December 3, 2013, in a game against the New Orleans Saints, the crowd roared at 137.6 decibels (dB), breaking the world record for the loudest outdoor sports stadium. (For reference, physical pain begins for humans who listen to sounds measuring 125 dB, and a jet flying overhead at a height of only 100 ft. hits about 140 dB.) But even taking into account crowd noise, Moskowitz and Wertheim were unable to find persuasive evidence that crowds on their own do anything to affect player performance.
Travel is tough on players, causing underperformance—FICTION
The theory is that changes such as adjusting to time-zone shifts and sleeping away from home disrupt players’ rhythm and cause them to underperform. But this theory doesn’t hold much water either. Moskowitz and Wertheim note that even when teams play “away” in their own city—examples include the Lakers versus the Clippers, both of Los Angeles (in basketball), or the Rangers versus the Islanders, both of New York (in hockey)—home-field advantage persists. According to the travel theory, home-team advantage should diminish in these cases, but it doesn’t.
Field conditions help home teams—FICTION
The theory that the home team benefits from acclimation to the home-field atmosphere is often given in reference to places such as the “Frozen Tundra” of Lambeau Field in Green Bay, Wisconsin, or the Mile High Stadium in Denver, so-called because of its high altitude, a challenge for visiting athletes. The theory contends that the Green Bay Packers are better prepared to play in extraordinary cold, while the Denver Broncos train in the thin air and are hence better conditioned to beat their opponents when playing at home. But this theory doesn’t hold up either. Cold-weather teams such as Green Bay do not show a statistical advantage playing in cold weather over warm-weather teams such as the Miami Dolphins or the San Diego Chargers. Moreover, home-field advantage remains for teams such as the Minnesota Vikings, who could benefit from cold weather but do not because their home field is indoors.
Home games are easier in terms of scheduling rigor—FACT and FICTION
This theory suggests that home games are often gentler on teams in terms of easier opponents or scheduling rigor. This does hold some weight, but only in certain circumstances. In the NBA, visiting teams play more back-to-back games with little rest in between than do home teams, so visiting teams in the NBA are sometimes more tired than home teams. Moskowitz and Wertheim report that, “Of the 20 or so back-to-back games NBA teams play each season, an average of 14 occur when they’re on the road. . . . That translates into one or two additional games you will lose each season on the road because of this scheduling twist.” The other case where scheduling rigor explains home advantage is in college sports, where home teams play “cupcake” games against inferior teams, especially early in the season.
Referees are biased in favor of home teams—FACT
The largest impact on home-team wins, according to Moskowitz and Wertheim, comes from a more insidious source: referee bias. They document cases of official bias, predominantly at “very crucial” points during the game, in baseball, American football, basketball, and ice hockey. But some of the most convincing evidence for referee bias comes from Professor Canice Prendergast who studied favoritism in the Primera División soccer league in Spain. (See “Are you blind, ref? Yes, in a sense.")