One of the most significant tools available to you (published author) when it comes to tracking your online sales, or lack thereof, is the use of the sales rankings provided by some of the most significant online retailers. In these systems, no 2 books can have identical ranking at the same time, and they come to a specific order by taking a number of factors into account.
One of the most significant factors that contributes to that ranking has to do with the number of copies sold in a period of time. Because of this you should keep in mind that movement does not always means sales, sometimes it means lack of sales.
When a book is first listed it doesn’t have a sales ranking, this is added only after the book sells at least one copy, however depending on the retailer, the absence of a sales ranking does not necessarily mean an absence of sales. While Amazon sustains a ranking system that includes every title that has ever sold a single copy,Barnes & Noble only list the rankings of those titles that have sold within a specific period of time.
When you sell a book your ranking jumps up significantly, however after a while your ranking begins to drop again due to the absence of new sales and then it jumps up again when you sell another copy. What occurs here is that, as time passes, your book goes from a book that sold a copy in the last week, to a book that sold a copy in the last month, to a book that sold a copy in the past two months and so forth. The longer the time, the lower your sales ranking (or higher, to be accurate, keep in mind that the smaller the number the better the ranking).
Check out Amazon’s biggest gainers in sales rank over the past 24 hours which is updated hourly at Amazon - Movers & Shakers.