BP's oil spill estimates and Amazon's rankings.

I've read quite a few articles about how rankings on Amazon are calculated and in light of the recent controversy over BP's inability to accurately assess the amount of oil that has been spilled from their leaking well and the amount still spilling, I've come to this conclusion: neither Amazon nor BP have any real way to calculate either the oil spill or rankings that show well your book is selling (or not selling.) Depending on what day you ask, you'll get an entirely different answer and it will generally come from someone else other than BP or Amazon (as we all know Amazon doesn't own a phone. ;))

Recently an author told me their book's ranking went from like 1,000,000 to like 20,000 overnight. I told them this meant they'd sold one book. They seemed to believe way more must have sold but I assured them this wasn't true. I know this because my rankings do that all the time and I know EXACTLY how many of my books I sell. I told them to be patient it will drop back down just as fast.

Also only books sold through Amazon make the ranking change. None of the books sold through other vendors do this. So if you're an author and you fall into the trap of thinking jumping up so many places at once means something--it does. It means you sold a book. That's it. ;)