Humans are great, they can do great things, as many of the tennis players proved at the 2024 Wimbledon Championships, but calling lines isn’t one of them.
Firstly, I give all my respect to all line judges, not just at Wimbledon but all around the world. When it comes to precision, it’s probably one of the most difficult jobs in the world, and it’s not a surprise, as the human eye is just not trained to see whether a ball flying 140 mph (225 km/h) scraped a bit of white chalk thrown onto the grass.
And that’s exactly the reason why substituting human line judges with live electronic line calling was one of the best decisions ever made. From the 2025 season, all tournaments on the ATP Tour should use the system, and this year’s Wimbledon proved why.
In the Gentlemen’s Singles draw, there were a total of 1,020 challenges in all 127 matches played, an average of 8.16 challenges per match, while in the Ladies’ Singles draw, there was a total of 512 challenges, with an average of 4.23 challenges per match.
Of course, with the incredible precision that these players play with, hitting lines very often, over a thousand of challenges in two weeks is not that surprising, but what’s quite alarming is the success rate of these challenges.
Out of 1,020 challenges in the Gentlemen’s Singles draw, 260 were successful and 760 were unsuccessful, that represents 25% success rate for the players, or in other words, 25% rate of incorrectly calling a ball for line judges.
While 25% doesn’t necessarily look like a big number, it needs to be put into perspective. First, there were dozens of challenges from players on balls, which were out by a lot, really a lot.
In addition to some wild calls for challenges, there is also a tactical aspect to using a challenge. With three challenges available per set, many players opt to use some in the closing stages of the set, even when they maybe don’t think the call was made incorrectly but just want to buy themselves some time to rest before the following rally.
If we say that there were a few tens of these challenges made, the success rate of the challenges immediately increases to the 30-ish range. And there’s more.
Another important aspect of the challenges to mention is that the vast majority of challenges are taken for rally-ending shots, as not many players want to risk stopping the rally, being incorrect on a challenge, and subsequently losing the point.
That means that there were likely many more incorrect calls, but no one ever found out, as they weren’t challenged by players. If we were really playful with numbers, all these factors could essentially push the line umpires’ success rate to 50%—a coinflip.
In a sport where every inch and every millimeter matters when competing for millions of dollars, pounds, and euros, a 50% success rate is hardly justifiable when it comes to calling the lines, and it shouldn’t be.
As great a job as every line umpire did at this year’s Wimbledon and every tennis tournament prior to that, humans are incapable of judging these balls.
If we consider that the error rate of a live electronic line-calling system starts with 0 and continues to decimal places, there shouldn’t even be a conversation about whether the live electronic line-calling system should have been adapted or not.
