Navigating the Amazon Sales Ranking

By Brent Sampson

When “Harry Potter and the Deathly Hallows” was added to Amazon’s Web site, it held an Amazon Sales Rank of #1 for months, even before it was released. This meant it was the top-selling book throughout all of Amazon. But what does being the “top selling book” on Amazon mean, and how does Amazon make that determination?

The algorithm Amazon uses to generate the Amazon sales ranking is proprietary, so the details contained herein are extrapolated from research and field tests. The resulting consensus finds that Amazon’s system provide marginal sales data at best and that, in most cases, the Amazon sales ranking is more akin to market research than anything else.

To whit, read Amazon’s own definition of its system, slightly paraphrased from their FAQ: “The Sales Ranking system exhibits how books are selling. The lower the number, the higher the sales. The calculation is based on sales and is updated each hour to reflect recent and historical sales of every item sold. We hope you find the Amazon.com Sales Rank interesting!” This last sentence seems to indicate Amazon’s own perspective on the importance with which the sales rankings should be viewed.

In other words, you’re not supposed to find the sales rankings informative or even helpful. You’re supposed to find them interesting.

In actuality, the process is somewhat more convoluted than they let on. The ranking does not depend solely upon the actual number of books sold, but rather, on a comparison against the sales figures of the other books in their database (all six million+ of them) within that same hour.

Current sales in that hour and historic all-time sales both play a role in the calculation. In fact, the predictive nature of the Amazon ranking system is what makes it possible for a newly released book to outrank an older established title, even though the actual total sales figures for the latter far exceed the former.

That said, sales history takes a back seat to current sales numbers occurring in a given hour. Sales projections and trending take an active role here, which is why a book’s ranking can leap from 900,000 to 1 in the span of 24 hours or less with a concerted marketing effort. Does this mean the book has sold nearly 900,000 copies in 24 hours? Absolutely not! What it does mean is that recent activity (i.e. purchases) for that book is trending higher than the 900,000 books it just surpassed. But, don’t get excited just yet; since the activity of 800,000 of those other books range from slow to stagnant, one or two orders are sufficient to catapult a ranking into the top 100,000 with “relative” ease.

If a book’s ranking breaks into the top 100,000, the sales history calculation starts to rear its head, which is why a “phenomenon” book has a hard time maintaining a high, legitimate ranking. A phenomenon is defined by a book that leaps from the high hundred-thousands into the lower thousands (or better) in the span of 24 hours or less, usually due to some concentrated marketing initiatives. Since Amazon’s sales history for that title doesn’t support the leap, the spike occurs and then quickly drops again. But that’s not to say such an endeavor doesn’t hold its advantages.   Phenomenon books that are well-written and well marketed can use its ranking “spike” as a foundation on which to base a consistent, respectable, long-lasting Amazon ranking. Does the ranking maintain the same zenith as its initial spike? Rarely. But, it also rarely drops into the millions again, either.

How does all this translate into sales figures? Unfortunately, since the data is recalculated all the time, it’s impossible to arrive at accurate, cumulative sales figures solely using the Amazon sales ranking. It fact, it’s work intensive just to arrive at an average sales ranking. This process alone involves the time consuming task of charting the ranking of a book at the same time every hour for 24 hours and then divide by 24 to arrive at its average daily ranking. Do that for seven straight days to arrive at its average weekly ranking. You can do it all month long to arrive at its average monthly ranking. The longer your average timeframe, the more accurately your sales ranking will reflect "reality" (as opposed to a spike or dip in sales).

Read other articles and learn more about Brent Sampson.

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