[CharlieVenkman]

When I woke up this morning, I was stoked to see that the rankings for one of my books went up overnight...but when I checked the sales for that book, there were none.  I figured it would show up sometime today, but no dice.  Anyone else ever have this issue?

 

[TexasGirl]

Rankings lag behind sales big time.
Or just a glitch. Amazon is known for its glitches.

I find it most amusing when I'm doing a promo and sell a couple hundred copies in a few hours and my next ranking change is worse than the previous. There's a definite lag until you hit the top 10,000 or so, then it updates much more regularly.

 

[jasonzc]

It happens all the time. You're actually seeing a bunch of other books lose ranking.

 

[Terrence OBrien]

The value of a sale declines over time. A book that sells 10 yesterday will outrank a book that sold 100 last month and five yesterday. We don't know the formula that values sales, but it is consistent with an exponential moving average.

My conceptual but dumb analogy: For each sale fill a paper cup with water and put it on a scale. more and more cups are on the scale as sales increase. The scale reading is the rank. But each cup has a small hole in the bottom, so water and weight continually leak away. The cup that is put on the scale today might weigh more than 20 cups put up there last month.