Interesting article by Dan Koboldt – author, bowhunter, and scientist – on his site
Few things are more obsessed-over by modern authors than Amazon Best Sellers Rank. For most of us, it’s a form of numerical torture, updated hourly. Although the precise inner workings of the algorithm are known only to Amazon, there are a few general accepted principles:
The more a book sells, the higher (closer to 1) its rank goes.
Rankings change rapidly, often moving thousands of positions within hours.
Paid and free books are ranked separately.
Beyond these basic principles, there is little certainty. The basic formula for Amazon Bestseller Rank seems to be sales over time, meaning that a book must continue to sell to maintain a high position on the lists. In theory, it might therefore be possible to achieve a high ranking if a book sold a modest number of copies in a short amount of time. I decided to test that theory with an experiment.
To see the results, click on the link or his photo below: