Is there really a home field advantage in sports?
Everyone's always talking about how great home-field advantage is in sports, but how important is it really? The mindless stats everyone repeats about how NFL teams with home-field advantage do better in the playoffs drive me crazy -- the teams earned home-field advantage because they're better already! Also, are the home-field advantages different in different sports?
I'm telling you, geniuses have sweated over this. Get a load of the opening from "The Home Advantage," a landmark study by Barry Schwartz of the University of Chicago and Stephen Barsky of Temple University (Social Forces, 1977):
This study relates to a perspective on group support whose origin is embodied in the work of [pioneering sociologist] Emile Durkheim. While Durkheim is best known for his stress on the inhibiting and restraining character of the moral community, he also [has a lot to say] concerning the stimulating effects of social congregation … For Durkheim … the very conditions which regulate man's passions and conduct are those which inspire and propel him to the most extraordinary levels of achievement.
In case it went by you, "the stimulating effects of social congregation" = home-field advantage, hereinafter referred to as HFA.
Durkheim knew whereof he spoke. Schwartz and Barsky say that, based on their review of hundreds of games played during 1971, the home team in major league baseball wins 53 percent of the time, in professional football 55 percent, and in college football 59 percent.
HFA in baseball has since been abundantly confirmed. In The Hidden Game of Baseball (1984), John Thorn and Pete Palmer calculate that the home squad on average plays .540 ball. A study of baseball HFA from 1901 to 2002 published in the Baseball Research Journal found "the average seasonal difference between a team's home winning percentage and its road winning percentage was .082." (In other words, an average team's home record is .541 and its away record is .459.)
Stats geeks in other sports aren't as obsessive as MLB's, but what research there is suggests HFA is common all over. Perusing a comprehensive recent study ("Long-term trends in home advantage in professional team sports in North America and England [1876-2003]," Pollard and Pollard, 2005), I note as follows: (a) since 1900, notwithstanding some year-to-year swings, MLB home-field winning percentages have been remarkably stable at about .540; (b) the NFL HFA fluctuates a lot, no doubt because fewer games means more statistical noise, but home-field wins are usually in the 55 to 60 percent range; (c) NHL home-ice wins have declined from 60 percent in the 70s to a pretty steady 55 percent since the mid-90s; (d) NBA home-court wins dropped from 65 percent in the mid-80s to 60 percent in recent years, still the highest of the U.S. sports studied; and (e) HFA shows up in UK sports too.
What explains HFA? Several possibilities are often cited, including familiarity with home turf, no travel stress, and what football fans call "the 12th man," the home crowd. But establishing what's most important isn't easy. Take familiarity — one study of 7 baseball, 17 basketball, and 13 hockey teams that moved to new stadiums (without changing cities) between October 1987 and April 2001 showed a significant reduction in HFA in the season following the move. However, other studies purport to show that MLB teams do better in a new stadium. One clear-cut case of HFA arising from venue familiarity is the Colorado Rockies, who consistently display the largest differential between home and away records of any MLB team. All agree that's because only the Rockies are acclimated to high-altitude Coors Field.
Crowd effects are easier to demonstrate, at least in some sports. A study of more than 5,000 English soccer matches found that teams scored an average of 1.5 goals at home vs only 1.1 on the road, with the difference growing by 0.1 goals per 10,000 spectators. The researchers attribute this to cowed refs' giving the visitors more penalties. Schwartz and Barsky thought crowd effects explained why HFA for baseball and football was lower than for hockey (in the 70s anyway) and basketball — the latter two sports are invariably played indoors, where the noise is more intense. Travel stress is probably a minor factor, since HFA persists even among teams that are geographically close.
How important is HFA? It certainly helps in the playoffs, where in major sports the team with the best record typically gets to play the majority of its games at home. During the regular season, not so much, and not just because pro teams generally play equal numbers of home and away games. Consider the Rockies. In 2003 the difference in their home/away records was an astonishing .296 — at home they played well (49-32), but on the road they sucked (25-56; 74-88 overall). As baseball-stat guru Bill James has pointed out, an undefeated team has an HFA of zip.