My sister in law, who is a professional horse-trainer just got dumped off a rogue horse the other day. She was wearing a helmet but she got hit hard enough to break the helmet, as well as some ribs etc. It is estimated that without helmet she would have been as good as dead.
(Me bad, never wore a helmet untill recently. First in a certain action where various stuff would rain over you, then as a fisherman at sea, where as working on deck requires a helmet, - mandatory for safety reasons, and proof for it's good is ample)