Crowd noise is a refereeing variable, not an atmosphere one

Home advantage survives in the numbers mostly because officials are human, and the games played in empty stadiums showed it plainly.

The romantic explanation for home advantage is that the crowd lifts the players. There is presumably something in it, and it has always been an odd claim, because the players who supposedly get lifted are professionals who play every week in front of noise and who report, when asked honestly, that they stop hearing individual voices about four minutes in.

The less romantic explanation is that the crowd works on the one person in the stadium who is making rapid judgement calls under uncertainty and has no video to consult in the moment.

When football was played without spectators for an extended period, home advantage did not vanish, but the disciplinary gap between home and away sides narrowed noticeably. Fewer away cards. Marginal decisions distributed more evenly. Travel, familiarity and pitch dimensions were unchanged; the noise was not. That is about as close to a controlled experiment as this sport is ever going to give us, and the result points at the officials rather than the athletes.

None of this makes referees corrupt or even bad. It makes them subject to the same social pressure that affects every human judgement made quickly in front of a hostile audience, and it is well documented that ambiguity plus volume shifts a decision towards the loud side. The effect is largest exactly where you would expect: penalty area incidents, second yellows, and added time in a game the home side is drawing.

The interesting question is what to do about it, and I do not think the answer is to pretend it away.

Video review has plausibly reduced the effect for the small set of reviewable incidents, since a decision revisited on a monitor away from the noise is a decision made under different conditions. It cannot touch the much larger set of unreviewable ones: fouls given, throw-ins awarded, advantage played, the rhythm of who gets the benefit of a doubt for ninety minutes. That accumulation is worth more than one penalty.

So when a manager complains that the officials were affected by the crowd, he is not making an excuse. He is describing a documented effect, badly, at the wrong moment, in front of a camera.

The honest response would be to build it into how we evaluate results. A point away is worth more than a point at home, and everybody knows it, and no table has ever said so.