Same statistic for motorcycles. You are more likely to be injured in a crash if you wear a helmet.

Because otherwise you go in the dead column.

Similar story for helmets during WW1. Prior to metal helmets, soldiers wore cloth caps. After the soldiers started wearing helmets, the number of head injuries climbed rapidly. The alternative, of course is that the soldier would otherwise have been dead.

You shouldn't follow up a source request with another unsourced fact, but let me follow up with yet another: the statistic are entirely different for motorcycles because motorcyclists are far more likely to have the type of accidents that helmets protect from.

Comparing the fatality rate of bicycling to the one for riding a motorcycle is not good.

edit: That's not only a claim that bicycle helmets vastly reduce the fatality of bicycle accidents (rather than just significantly reduce them), but a claim that so many unhelmeted riders die from bicycle accidents that it distorts safety figures. All of this without any safety figures.