do you mean of a certain series of books?
because is you mean of all slabs of every series of every book/slab out there? it wouldn't even top out at 1% so I'm confused. There are 10,000 hulk 181's slabbed alone, and if there is a perfect 10 there is only 1 or 2, I'm not looking it up to double check. Assuredly there are too many series/books/slabs etc that have thousands slabbed, multiply that by the 1000 books/slabs? and were talking an "nth" of a 1% so i'm not sure if that is what your asking?
now a book like Last Ronin #1? or Batman Damned? then the percentage of total of those series alone, could possibly be more than 1% but not by much