everyone being forced to wear helmets is not the same as everyone choosing to wear helmets. I suppose the data would be different if the later were the case.
As many here are pro helmet and not pro compulsion that is what you should be referring too.
Do you have data on that?
Not sure why you think people being force to wear helmets rather than it being voluntary makes a difference. Whether its consential or not, if helmets really did protect, the large drop in unhelmeted cyclists should, if you and others were correct, be accompanied by a large drop in cyclist head injuries. But it isn't. Moreover in the case of Ontario where the law was not enforced and wearing levels dropped back to pre-law levels, head injuries did not increase either.
But the non- compulsion data is available. For example Hewson's two studies on the UK datasets. He found no evidence of a safety benefit from helmet wearing in either adults or children. Also Rodgers review of 8 million cyclist accidents in the US over 15 years that found that helmeted cyclists had a higher fatality risk than unhelmeted ones.