What would empty stands, partial crowds mean to betting lines and NFL, college football games?

Adam Burns didn’t fully understand the power of the Seahawks’ home crowd until he experienced it for himself last year. The roars were so loud he couldn’t hear the colleague in the stands next to him.

“It definitely did make an impact on the game, I would think,” Burns said.

How much of an impact? That’s not clear. But it’s something oddsmakers like Burns are trying to figure out.

As society reopens in the COVID-19 era, NFL, MLB and college football teams have discussed home games without fans or in partially filled stadiums. If that happens, Burns — the sportsbook manager for BetOnline.ag — will have to adjust his betting lines. He just doesn’t know how yet.

The conventional wisdom is that a home-field advantage in football is worth three points, although that can go up slightly for a notoriously tough environment (like New England) or down slightly for a notoriously tame one (like the Chargers). Crowd noise contributes to the spread, but it isn’t the only factor. Denver’s mile-high altitude helps the Broncos and Rockies no matter how many fans are in the stands. The pandemic probably won’t alter the way cross-country travel affects college football players’ body clocks.

So if the only thing that changes is the noise in the stadium, how will that change the results? Oddsmakers have a few guesses.

“I think penalties is a big one,” Burns said. “I think there will be less.”

Anecdotally, the logic makes sense; loud crowds can spark false-start penalties by drowning out an offense’s snap count. Statistically, some studies have suggested home teams are more likely to benefit from referees’ close calls, possibly because of the subconscious effect of crowd noise.

Other factors are trickier to predict. Burns said scoring could decrease, either because players are less motivated with no one to play in front of or because the pandemic has kept them from training properly.

Sascha Paruk sees it the other way.

“My instinct on that is in the NFL, it’s going to go up because the road offense won’t have to deal with crowd noise,” said Paruk, Sports Betting Dime’s lead oddsmaker.

Neither Paruk nor Burns expect a big change in baseball, where crowds are more subdued and the home-field edge has historically been small. But games could swing more in college football if massive stadiums are only partially filled.

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“If you’re taking out half of that noise, I think you’re taking out a huge part of the sort of motivating environment, which very tangibly has a bigger impact on college kids than it does pros in the NFL,” Paruk said.

Although the sports world has already witnessed some fan-free events since the pandemic began, Paruk and Burns don’t think there’s enough data to measure the change.

Paruk said we might look back at a German soccer result — Bayern’s 1-0 win at Borussia Dortmund last week — as “the harbinger of what was to come” because the road team won in an empty stadium that normally would have been boisterous. Or it could have been just one random result.

That’s why Paruk and Burns are waiting to see what happens before they start changing the way they approach lines. They’re treating their spreads as traditional home games rather than neutral-site matchups until they get more information about how players —and bettors —respond to empty or half-empty stands.

“It’s the same as everything else in life right now,” Burns said. “You go day by day and see what happens.”