Do you happen to know the overall change in accidents? That's the big question behind the motivation for this change. There's no doubt that helmets would reduce the percent of all accidents that are head related, but does some reduced concern about safety result in more accidents overall?
From the biggest Ski insurance/interest group in Germany (the ones from the Ski federation), the stats show a 50% decrease since the 80's.[0]
The trend is stable/slight increase in the past 5 years.
For the head injuries, it reduced from 2/1000 skier to about 1/1000 skier/year. It follows the general trend of the number of accidents per skier/year.
Looking at the material and the quality of the slopes in the past 40 years, they are definitely a big driver of this change, they improved a lot!
