Home advantage wasn't an accident for Jeff Beck, the Cambridge United manager in the '90s because he used groundsmanship as a weapon:

- plough the pitch to kneecap expensive teams with running/passing games

- narrow the pitch dimensions to minimise fancy wide plays

- grow the grass long and pour sand in the corners so long balls less likely to go out

He then recruited the tallest forwards he could and the strategy was simple, hoof it to the big fellas up front. None of this running/passing nonsense that requires money/talent.

I expect regulations might have improved since then...

It’s surprising what range of pitch size and slope are allowed in professional football.

https://en.wikipedia.org/wiki/Football_pitch

While FIFA recommends a specific size for pro teams, a legal pitch can have widths range from 46 to 91 metres and lengths of 91 to 119 metres. That’s a possible ratio range of 1:1 to 1:2.58.

I could imagine that stadium upgrades have meant that pitches don’t have as much variation as in the past too.

Tobias J. Moskowitz, a UChicago Economist, and L. Jon Wertheim studied home field advantage across all sports years ago, and concluded referee bias was real and was the driving force behind home advantage. It's explained in the book "Scorecasting"

For me, their findings were vindicated during the pandemic, when HFA all but disappeared. My guess is more recent decay might be because of VAR and goal line technology, which have become more integral to the game in recent seasons.

The dataset you need is the PL2 or academy matches. I don't think anyone shows up to those games, but the players are vying to be full premier league professionals. So travel arrangements would be similar, physical fitness similar, tactics similar, but there would be no fans.

As for the time trend, I suspect professionalization was happening slowly, then quickly. Of course there have been fully paid footballers for a long time, but if you look at stories from the 80s and early 90s, the guys would still smoke and eat burgers. It's only in recent decades that the stops have been pulled out, and everyone started doing full on sports science to maximize every chance.

Having absolutely everyone optimized physically also means you can explore strategies that used to be impossible. If you know you're at 80% due to traveling, your gegenpress is going to be a bit less attractive.

It'd be interesting to plot this against incidences of fouls and misconduct over the same time period. If play has gradually gotten cleaner, this would provide less opportunity for referee bias to affect outcomes even if referees themselves are not becoming less biased over time.

It would be useful to compare with other leagues where home field advantage is significant. I do not have any data but as a football fan I suspect the following variables are important:

- England is an homogeneous country in terms of geography. There is no 40C degree temperature difference between north/south clubs. Playing in weather conditions one is not used to can affect the away team.

- England is also a small country. The away team can arrive at the stadium within the day. Not only it means they are better rested but also home fans cannot bother them at the hotel making noise, throwing fireworks, etc. preventing them from sleeping.

- The FA is not as corrupt. Sure, certain teams can get away with playing dirty, but in general referees will show red card to a home team player, or call out a penalty for the away team.

- Less threatening environment at the stadium, both for the away team players and the referees. Nobody is throwing food, beer or anything at the players during the game, and hooligans will not try to harm the referee if the home team loses.

> Given that the “only” COVID difference is the absence of supporters

I think the potential confounders (training was disrupted for months, games were played in summer months, season was compressed, etc.) make that "only" do far too much work here.

There was an article, I can't recall if it was a reliable source, that said the home field advantage is vanishing because "before" if many players were playing away they'd take advantage of their being away from home by going out, getting drunk and staying out late in the hope of taking one or more people back to their hotel. These days, if you're a star athlete you can live on Tinder and fairly reliably have someone turn up to your hotel room. You stay reasonably sober and get an early night.

I'd not be surprised to hear that this is complete nonsense, but it's a memorable story. A simpler version of this story is that people have steadily drunk less since WW2 when going out, and you're more likely to go out when away from home.

What I want to see is an analysis of how likely it is that the winner of a match/tournament is also the best team. Basically attaching a p-value to soccer. Then analyze how the rules of the game can be changed such that this p-value is increased.

I've looked at this question in Rugby Union. In my opinion. The travel issue is the main factor for home advantage. Travelling is physically and mentally tiring. If you can ease the travel methods. Where you either cultivate a team environment where people will be at ease being away from home / home base. Or travel earlier and in better form. Then you will end up with better away results.

I've listened to Lee Dixon and Graeme LeSaux talk about this when they're commentating on matches and how when they were at home they knew exactly where they were on the pitch by a combination of the same fans/advertising hoardings/stand structure which helped their game

I remember the COVID football days. Soulless games taking place in echoey, empty grounds seemingly for no reason at all. Little wonder the home team advantage fell off. Football without fans is nothing.

Home advantage is interesting to me because of it existing in essentially every sport and it's almost always small enough to not matter a lot but large enough to notice. Lots of factors are attributed but I've never seen someone try to analyze those factors.

You could probably do some minor rules tweak to get rid of it or reduce it further - but I think it's actually a good thing to have a noticeable but small home advantage. You have the same number of home and away games so it evens out in the regular season. So a little nudge for the team that everyone bought tickets to watch seems alright.

I think it's desirable in the playoffs too, even if your goal is for the best team to win the tournament, not just from an entertainment perspective. We deliberately stack the playoffs for the teams that did best in the regular season, both by seeding and by who gets home advantage. There's lots of entertainment reasons this makes sense to me, but it also makes sense to me in terms of making the best team most likely to win. The playoffs are usually less data than the regular season. So this is a way of letting the regular season data have more of an influence on the outcome of the championship.

from another study, the home advantage is due to ref's unconscious bias, rather than an effect from the public. So all the new tech (VAR) surely has helped reduce that bias.

My first thought was that maybe fan culture and atmosphere has changed, which would have a more noticeable effect in the higher leagues, because lower leagues are still hilarious [1][2]. But the home advantage seems to affect all leagues the same, so I am probably wrong.

[1] https://www.youtube.com/shorts/KXmv7VK_110

[2] https://www.youtube.com/shorts/aTHc9Xinb6U (uncensored: https://www.tiktok.com/@bunch_amateurs/video/733659771889629... )

Home field advantage is a real thing and is measurable. Strikingly, it's been declining steadily and consistently since WWII. The charts in the blog post are interactive and you can zoom into the data.