This is an easy step that soccer has taken to reduce the occurrences of brain injuries. Anyone who is confused on this issue should note that any jostling of the brain can cause minor, short-term brain damage. It's bad enough to bounce a relatively soft soccer ball off your head to warrant removing the practice from the sport, especially for younger players.

Other sports, like football, present a much harder challenge. Even if you remove direct head contact as a variable, most aspects of tackling can result in concussions. The reason football is uniquely controversial is that minor concussions are mostly inevitable and severe concussions are commonplace.

By contrast, the most likely way to get a concussion in soccer is to head the ball, which isn't fundamental to gameplay. In any sport, you might run into another player at high speed but that's not typically a core part of the gameplay. Football is controversial because it's hard to fix.

> The possibility of concussions is present in [nearly?] every sport

Tennis, golf, swimming, weightlifting, etc - probably have a pretty low incidence of concussion. Stuff with teams and fast movement are probably most suspect; hockey and football would intuitively seem like the worst offenders.

In 2016 (in the US) 1.08 million students participated in high school football while 821,851 participated in soccer.

I don't have stats available for middle school, but earlier than that the players don't hit nearly as hard, as they have considerable lower mass and speed.

Not sure where your 3x number comes from, but I don't think we need to include YMCA recreational league soccer any more than we need to include flag football.

Unfortunately n, in this paper, doesn't seem to mean sample size like you would expect in statistics. It is an extrapolated number of concussions nationwide based on a study of 100 high schools.