all they have to do is add more sugar to make up for the missing hazelnut
 replies(1): 
I think a combination of bad cocoa harvest and previously a bad hazelnut harvest have altered recipes globally to be more sugar and fat and even less cocoa and hazelnut, but it's hard to find any recent comparisons.
Maybe you have a link? I don't speak any languages from behind the Iron Curtain where the impact is probably the most obvious, so I would appreciate a good link.