re: I don't understand
I used to think you were smarter than that, Tom.
There would have been ample evidence had the ozone layer fluctuated as much as you are suggesting in the last couple of hundred years... changing rates of skin cancer, different survival stats for amphibians, etc. But it's a new thing, CFCs et al are proven to destroy ozone and to move to that part of the atmosphere... what do you want???
And by the way, it's not really just a "hole" like the hole in your socks with defined edges... the layer is thinner in other areas as well, resulting in increased UV, so don't throw away your sun screen just yet.