Do supporters in the grounds affect results? Some evidence from Austria.

Remember when we (myself included) declared the end of home-ground advantage after football restarted? Well, not so fast. At least in the Austrian Bundesliga, things are pretty much back to normal, although we are back to closed gates after some games with fans in September and October.

We can see that away teams were actually slightly more successful even before the pandemic halted football for almost three months. They obtained around 0.1 points per game more than home teams in the 22 games before lockdown. This difference skyrocketed after restart to almost 0.5, which is generally why home-ground advantage was supposed to be at least severely damaged. Things have however changed since the start of the current season. Home teams obtain around one point more every five games than their opponents. Roughly the same is true for the number of goals scored. 

 

Interestingly, the pattern is almost identical for home and away teams if we look only at goals scored in the first half: a massive drop after restart and comparable levels in the 2020-21 games to the ones with full attendance. This also means that away teams completely outperformed home teams after the break in the ten matchdays between restart and the end of the season. Whether this is due to the absence of supporters and psychological effects thereof or just some random variation is unclear. 

Underlying statistics show a similar, although less contrastive picture. Home teams suffered a significant drop of performance levels after football restarted, both in terms of shots and expected goals. Games were almost completely level between home and away teams; hence the absence of home-ground advantage can be confirmed for this period. Interestingly, also away teams suffered a drop in expected goals after restart yet is was much smaller than the one for home teams.

 

 Since the start of the current season, things are however back to comparable levels to before the pandemic. Both home and away teams actually create around 0.1 xG per game more than before football was halted, hence the difference between them is basically the same. The question why all teams create more or better chances now than at the same time last year would be an interesting question for a separate thread or blog entry. In line with what we saw when looking at actual goals scored, analyzing expected goals shows that away teams massively outperformed their opponents especially after half-time.

One decisive point why away teams performed substantially better after restart was discipline. Referees seemed to punish them much less than before Covid, both in absolute terms as well as in comparison to home teams.

This pattern was somehow reversed after the start of the 2020/21 season. Not so much in terms of penalties, where away games are still treated preferably, although the difference between home and away teams is at the moment minimal. They still get around one penalty more every eight games, this difference was around three times higher in the final games of last season. Both get more penalties now than last season; the pressure on referees to award penalties is at least in this case negatively proportional to the number of fans in the stands.

 

Likewise, the conversion rate of penalties is much higher this season than last and also way above the long-term average of around 0.8. More than nine in ten penalties are converted this season, and the difference between home and away teams is again small. As in the case of penalties awarded, home teams suffered greatly after restart and are now at higher levels than they were before the pandemic.

Other disciplinary topics show more diverse patterns. Offside calls have been on the rise ever since, something I would not directly link to the number of spectators in stadia. These are (despite some confusing VAR cases) obviously more objective, binary decisions than fouls, cards or penalties.

 

Fouls and personal punishments were in my opinion the main drivers of away teams’ improved results after lockdown. In all three categories (fouls, yellow cards, send-offs), home teams were treated worse than their opponents in the ten rounds after football restarted, unlike before Covid. This pattern was reversed but for players sent off (both straight reds and second yellows), where they are still worse off. In all cases, the difference is however smaller than it was when fans where still allowed without restrictions, which would indicate that having full grounds does influence refereeing decisions.

So, do supporters influence results? To answer this question, the current scenario offers us nearly a natural experiment. Until matchday 22 of the past season, they were allowed without restrictions. After that, games where played completely behind closed doors until the end of the season. Then in summer, there was an initial limit of up to 10.000 visitors, which was in place however only for matchday 1 due to growing infection numbers. This limit was subsequently lowered to 3.000 and then 1.500, before the league had to return to closed gates. Under each scenario we had a couple of games played, although with a limited sample size, so conclusions should be taken with a grain of salt.

 

We can see that point average for home and away teams was relatively stable before a few games before football was stopped, with away teams overperforming their counterparts during a long time early in the season. They then started to perform worse, but immediately rose again to levels unseen before after restart and maintained this level for the rest of the season. With the return of fans, their performance levels dropped again and reached a low point a few games in the 3.000 supporters period. They then started to rise again and have reached parity with home teams lately, as one would suspect if we are to suppose that the presence of fans influences results for the teams they support. Evidence is not really robust, but we can definitely show that away teams performed better with lower attendance figures or no fans at all in the stadia.