Football Manager is one of the most popular sports video games in the world. The 2019 version was a chart-topping hit in the UK, where the game is most widely played. Previous versions of the game have consistently sold more than a million copies each.

Football Manager allows fans to simulate the experience of managing a professional soccer team at a level of extreme detail, with hundreds of thousands of players from clubs in more than 100 leagues from 50 countries coded into the game. In addition to choosing your squad and strategy, you also have to deal with the media and the emotions of players. Unlike in most sports games, gamers don’t actually play the matches, though they can watch them and make strategic adjustments during the game. Football Manager is considered so realistic that it has been used by English Premier League teams for scouting, and by managers to improve their skills.

The game appears to have a racism problem.

In addition to rating players for physical skills like agility, dribbling, and strength, players and team staff are scored on non-physical attributes like sportsmanship and loyalty. Ratings are given on a 1-20 scale, with 20 being best. The game uses a huge network of scouts to generate these ratings for hundreds of thousands of players and staff across the world, but the final ratings are approved by the game’s approximately 100 head researchers, according to the Telegraph.

Among the many physical attributes assigned to players and staff, including things like hair color and length, one measures the darkness of their skin, with 1 being the lightest and 20 the darkest. For example, Russian forward Alexandr Kokorin is a 1 and Senegalese midfielder Badou Ndiaye is a 20.

A Quartz analysis of Football Manager’s data found that players and staff with darker skin tend to have worse ratings on non-physical attributes. Using data found in the Football Manager Editor database for 2019, we examined the share of players and staff with each skin color number who received a rating of 10 or above on sportsmanship, temperament, professionalism, and loyalty—that is, those who rank in the top half of scores for these non-physical attributes. Only players and staff who had been with their national team for at least 25 matches were included in the analysis, to assure that it was based on prominent people. The data include about 4,800 players and coaches.

As the chart below shows, on each attribute, players and staff with lighter skin are more likely to receive a score of 10 or better. (The relationship was first pointed out by Football Manager player Evan McFarlane on Twitter.)

To test whether this wasn’t just inter-country differences, or specific to team staff, we also analyzed the professionalism ratings of more than 900 players on English Premier League team rosters who are currently making more than £1,000 ($1,270) per week (thereby excluding young academy players who are unlikely to appear in a Premier League match). Again, we find that lighter skin players tend to receive higher scores on non-physical attributes: 72% of players assigned a skin tone of 1-5 received a professionalism score of 10 or better, compared with just 55% of players assigned a skin tone of 16-20.

The results of this analysis won’t come as a surprise to black players like English forward Raheem Sterling, who has spoken out about the way black players are treated by the media and fans. Sterling recently called for tougher penalties against teams whose fans shout racist abuse at players, a regular occurrence, suggesting it should impact that team’s place in the standings. In this context, it is perhaps not surprising that racist attitudes seem to have bled into soccer’s most popular management simulation game.

Quartz contacted Sports Interactive, the company that develops Football Manager, for comment and received no response.