From author Dan Koboldt:
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 assess the impact of rapid sales in a short time frame, I organized a coordinated buy of The Rogue Retrieval on May 12, 2016. Importantly, I didn’t make any purchases myself, for two reasons:
- I’d already bought the e-book for both of my Kindles, so Amazon wouldn’t let me.
- I didn’t want to appear to be gaming the system, or “buying the bestseller list” as is common practice in the business nonfiction world.
Instead, I turned to friends and fans, most of them fellow authors, who were willing to help. More than 50 people stepped up, and agreed to purchase the Kindle e-book at a specified time on that day. We targeted 8:00 a.m., which meant that some who live overseas bought at around midnight, NYC time (morning for them).
Here are some questions that I hoped to answer:
- How long does it take for Sales Rank to reflect new sales?
- What rank could be reached with 50+ sales in a single day?
- What’s the effect on subcategory rankings?
. . . .
The first twenty-four hours into my experiment offered some insights:
The first boost (2 hours) came from sales the day before, when some eager volunteers pulled the trigger a bit early. The two main peaks occur at hour 7 (European volunteers) and hour 16 (US volunteers). Thus, the lag isn’t quite 12 hours as I previously believed, but closer to 8 hours.
. . . .
In total, about 57 people bought The Rogue Retrieval within a 24-hour period. Although we targeted 8 a.m., sales continued throughout the day. The rank peaked about noon the following day at 4,748 in the Paid Kindle Store:
It might surprise some that so many sales only propelled my book to #5,000, but this speaks to the size of the Amazon bookstore. If we assume it ranks 1 million books (an underestimate), this ranking is in the top 0.5%.
Notice another property of Amazon Sales Rank: increases happen quickly (as “jumps”), whereas the post-sale decrease in rank happens more slowly. Especially for the first couple of days. After 72 hours, however, the drop-off becomes more precipitous. This seems to support something I’ve read about Amazon’s internal ranking algorithm: sales from previous days carry some weight. The window seems to be 48-72 hours.
Link to the rest at Dan Koboldt and thanks to Ann for the tip.
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