When setting a line on an NFL game, or any game for that matter, oddsmakers rely heavily on their power ratings. By comparing the ratings of any two teams, sportsbooks can decipher roughly what the spread should be. Once they come up with a number, oddsmakers will make adjustments to the line, including injuries, weather, head-to-head matchups and most of all, home-field advantage.
Generally speaking, home-field advantage is worth roughly 3 points to the spread in the NFL. For example, if you have two evenly matched teams, they would be a pick'em on a neutral field. But if one team was playing in their home stadium, they would be deemed a 3-point favorite.
Home-field advantage has become a topic of conversation lately as the NFL and other major sports leagues are coming to the realization that, unless something major changes, games will likely be played in empty stadiums for the remainder of the year due to coronavirus concerns. According to broadcaster Joe Buck, Fox and other stations are considering pumping in fake crowd noise and adding virtual fans in the stands to improve the television experience for viewers.
For bettors, we must think about how no fans in the stands will affect the product on the field, court or ice.
The NFL has been and always will be the king of betting. It's the most popular sport and generates the most action, especially among casual or public bettors. Average Joes love betting on favorites and home teams in the NFL. It's pretty simple. They want to bet on the "better" team and the team that enjoys the support of their raucous home crowd. However, sportsbooks know the public gravitates toward favorites and home teams and, as a result, they shade their lines further toward the popular side, forcing public bettors to take overpriced numbers. In turn, this creates value on backing unpopular road teams, especially road underdogs.
Since 2003, home teams have won 57.2% of their games during the regular season (according to Bet Labs Sports). In the postseason, home teams improve to 61.8% straight up. However, covering the number is a different story. In the regular season, home teams have only covered 48.7% of the time. In the playoffs they dip to 47.6% ATS.
Translation: Home-field advantage is real but it's overrated. Home teams win the majority of their games but cover less than 50% of the time.
In a recent CBS Sports article, several researchers suggested that home-field advantage isn't as much about the crowd noise on the players (pumping up the home team and throwing off the visiting team who can't hear the snap count), but rather it's effect on the referees. More closely, the refs make more favorable calls to the home team and are influenced by the pressure of the crowd. According to NFL referee John Parry, sustained booing plays the biggest role. "It does affect your psyche. And you wish at times you could crawl under a rock..."
So how will no fans in the stands affect the betting line? I reached out to a pair of oddsmakers and got roughly the same answer.
Chris Andrews of the South Point: "I think the home field means about one point. Even that might be a stretch, but I think it means a little something."
Chris Bennett of Circa Sports: "No fans in the stands is probably worth about one point to the spread."
In other words, if a team would normally be favored by 7 points with a stadium full of fans, that same team would be roughly a 6-point favorite this season if the stadium is empty.
One thing to keep an eye on when it comes to road teams this season: divisional underdogs.
We see a big difference in road dogs covering the number inside the division vs. outside the division.
Since 2003, road divisional dogs are 53.3% ATS. On the flip side, non-divisional road dogs are just 50.5% ATS. Why do road divisional dogs cover at nearly a 3% higher clip? First off, the public loves betting home teams and favorites, which provides value on road dogs. However, the divisional element is key. Divisional opponents play each other twice per year. This leads to a built-in familiarity, with each team knowing the opposing players, coaches, stadiums and tendencies. This levels the playing field and benefits the team getting points.
The best time of year to target road divisional dogs is in September. They've gone 56.7% ATS since 2003. Early in the season divisional dogs bark loudest because they're healthy and hungry and the favorites haven't hit their stride yet.
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