Colorado sports fans have heard all the jeers.
“How do you breathe up here?”
“Our boys aren’t used to playing at this altitude!”
“It’s not fair, your players LIVE here!”
For many, the idea of playing Denver teams at altitude remains an interesting part of sports mysticism. Some claim the significant difference in elevation gives Denver-based teams a distinct home-field advantage, while others think it does not make any difference.
Those who believe in the advantage point to the fact that the Broncos have the best home record since 1975, and note that certain players, such as former Pittsburgh Steelers safety Ryan Clark, being unable to play in Denver in the past due to various health conditions.
So, is the legendary altitude advantage actually a real thing? Analysis of Denver’s largest sports teams suggests otherwise.
The Broncos, those of the best home record in the NFL since 1975, have actually performed slightly below league average at home since 2002. When adjusted for strength of record per year, the Broncos have actually won two games less than league average over the past 15 seasons. The Broncos performed at a league-average rate at home in eight of the 15 seasons analyzed and only deviated from the average by more than one game once — when they lost two more home games than average in the 2011 season.
Ultimately, such a small margin of below-average performance is not going to affect the Broncos’ season-to-season performance, but the numbers demonstrate that the Broncos are a league-average team at home and that any altitude advantage they might have does not reflect itself in the wins column.
But what about the other Denver teams?
The Rockies, on the other hand, provide far more interesting data for consideration. The sluggers from Coors Field have performed above league average at home since 2002, having won 49 games more than league average over the past 15 seasons (after adjustment for strength of record). The Rockies exceeded the league average for their home win record in 13 of the 15 seasons analyzed, deviating from the average by more than six wins in 2002, 2003 and 2014.
However, the Rockies’ numbers are a bit inflated when compared to those of teams from other sports because baseball teams play far more games than any other sport. In comparison, the Rockies play about twice as many home games as the Nuggets, and more than 10 times as many home games as the Broncos. So in reality, while winning three more home games than league average every year would provide a massive advantage in football, it is not particularly significant in baseball.
Furthermore, because the sample size for home games is so high in baseball, it would take an even-greater above average home win margin to establish a statistically valid concept of an advantage season-to-season.
So while winning three or more home games than average a season (which they have done in seven of the past 15 seasons) might seem significant in the Rockies’ case, it would take a consistent performance above average by at least eight wins — something they have only done twice in the past 15 seasons — to substantiate an argument for a competitive advantage. Three extra home wins, the Rockies’ average performance above league average, constitutes less than 5 percent of their home games.
The Nuggets are another example of this. They have performed above league-average at home, adjusted for strength of record, for the past 14 seasons since 2002 (not including the current 2016-2017 season), but have not done so at a statistically relevant level.
The Nuggets have won 16 more games than average for their record over the past 14 seasons, which amounts to a little bit more than one win over average every season. That is not nearly enough to be statistically significant or to make much of a difference in their performance season-to-season, as one win at the Pepsi Center comprises less than 3 percent of their total home games.
So from a statistics standpoint, the case would seem to be clear: Denver teams do not have an unfair advantage at home. However, the famed altitude of the Mile High City still impacts athletes. Its effects, though they may not be reflected in the win-loss column, can still affect games.
The case of former NFL player Ryan Clark stands out as a particularly relevant example.
Clark grew severely ill after playing in Denver in October 2007. He was hospitalized overnight and eventually shed 40 pounds and had to have his spleen and gallbladder removed due to the illness.
Clark has a genetic blood condition known as sickle cell that is known to leave athletes affected by it at greater risk for heat stroke and muscle breakdown than other athletes when exercising in extreme temperatures or altitudes. Because of the incident, Clark, a star defensive player on the Steelers at the time, was held out of subsequent games in Denver.
Clark’s story is significant because his sickle cell condition (not to be confused with sickle cell disease) is not that rare, affecting over 2 million people in the United States. While Clark’s story may be one of only a few to receive significant publicity, he is assuredly not the only professional athlete whose health is put at risk by competing at altitude.
Altitude impacts athletics, even if it does not come close to influencing the outcome of sports games. The namesake elevation of the Mile High City is enough of a factor that speculation over the true scope of its impact is likely to continue for years to come.
As far as giving Denver teams a home-field advantage, though, the numbers do not lie: the altitude advantage is a myth.
Enterprise Editor Sean Kennedy can be reached at firstname.lastname@example.org or on Twitter @seanskenn.