New Research Shows Football Referees DO Have a Home Team Bias

Referees Cards and Whistle on GrassAs the new football season gets into full swing, punters are starting to plot how they are going to profit this term – especially now that fans have returned in full capacity to stadiums.

How will that manifest itself? Will there be more goals? Will there be more late goals as supporters urge their team on to find an equaliser or winner? Will we saw more home wins than we have during the rest of the pandemic period?

We’ll only know the answers to those questions in the fullness of time, of course, but new research has identified one interesting dynamic that punters can use to their advantage.

A study conducted by the University of Salzburg has found that referees are biased towards the home team – but only when there is a crowd present.

Most pertinently, this bias manifests itself in the quantity in which they show yellow cards to home team players – there is a lower probability, some 26% in fact, that the ref will book a home player for a late tackle or dissent when they are being heckled by a partisan crowd.

The paper, written by Michael Christian Leitner and Fabio Richlan, has been published online at the Frontiers In site, and the piece’s title – ‘No Fans, No Pressure’ offers an insight into how the beautiful game changed during behind-closed doors matches.

The researchers took a look at more than 1200 games played across Europe – half during 2018/19 season, and the other half in the midst of the restrictions of fans in stadiums in 2019/20.

Amongst their results, they found that the home win percentage decreased from 65% to 53% without fans present, the average number of goals per game dropped from 2.80 to 2.35 and the number of cards was higher without a crowd.

So, punters may want to reconsider their betting options for 2021/22 – more home wins, more goals and fewer bookings!

Testing the Numbers

Red Empty Folding Stadium Seats

At the time of writing, we’ve only had one completed Premier League gameweek, and so we don’t want to be lulled into thinking such a small set of numbers has any consequence.

But it is worth at the figures from Gameweek 1 to see how they compare to the pre-Covid days (remember them!?) and during the pandemic.

Here’s a table that shows the average number of yellow cards per gameweek, per season in the Premier League, using data from the competition’s official website:

Season Bookings per Gameweek
2021/22 21
2020/21 29.6
2019/20 33.7
2018/19 32.2
2017/18 30.6

As you can see, the data doesn’t quite match up with what the erstwhile researchers found.

However, some interesting observations emerge. The most yellow cards per gameweek in recent Premier League history came during that chaotic campaign ending 2020, where nobody knew what was going on and the action wasn’t completed until July.

And the lowest? Of course, we only have one week of data to use, but the opening round of games this season yielded an average number of bookings that was far below that experienced during the past five years.

That number will likely increase across the campaign, but still the original hypothesis might just hold true – with fans in the stands, the number of yellow cards issued diminishes significantly.