As a mathematician, your use of percentages with ordinal numbers offends me. If I am ranked #2, and you are ranked #1, it does not imply that I am two times worse than you are, or that you are 50% better.
A move from 7 to 14 is a 100% move, not a 200% move (14 - 7)/7 = 1 or 100%. But of course, you can't do that with ordinal numbers because the fact that Boortz is now at 14 does not mean his sales or his books popularity have fallen 100%.
Still not correct. If he had a 100% drop in sales that would be zero book sales.
When your sales are rising you can have greater than 100% sales, but on the way down you can't go above 100% and the only way to hit 100% drop in sales would be to hit zero sales.