I think they have about 100k living there, say 15% for kids 0-13, 15000, say 6% cycling to school, 900, if 80% already wear them, 720, 180 not.
So, they introduce a law, with fines, police time, to force 20% (180 extra to school) of kids to wear them, taking away choice for 15000.
The outcome may not be measureable in the short term, based on the data size limitation, but the effects will probably be small but in the same direction. In the long term a number of factors come into play, inconvenience, enjoyment, freedom, not having a police threat in a day to day activity with a low risk of serious head injury, comparing to countries with the free choice and personal liberty to choose etc. If other parts of the British Isles do not follow, Jersey will have lower levels of civil liberty that they have imposed on their children, using misleading claims and information.
If accident cases arise and not wearing a helmet, discrimination in compensation may result, compared to pedestrians or indeed motor vehicle occupants who suffer similar head injuries.
This sub-forum all discussions about this "lively" subject. All topics that are substantially about helmets will be moved here, if not placed here correctly in the first place.