Of rape claims. I think much of the range comes from the low numbers being claims that didn't get washed out very early on, the high numbers including cases where the cops promptly figured out she was lying, often before charges were ever filed.
I think this is one of the statistics which are made up on the spot. When the number of actual false rape claims are compared to the number of unreported rapes, it would have to be a very small percentage.
I'll stand firm on my claim that the source of this sort of thing is an irrational fear of women's sexuality.