Tuesday, December 4, 2012

The Amazon Book Jungle

Tracking the elusive book rank
in the Amazon Jungle.

My new book, Taxes in America: What Everyone Wants to Know, with Joel Slemrod, was published a couple of weeks ago and like book authors everywhere, I’ve been obsessively tracking its rank on Amazon.  At the moment, it is at 12,368, which doesn’t sound that great, but Amazon has millions of books, so Joel and I are firmly within the top 1% of book sales, at least for now.  The book is atop the tax law category, beating out such volumes as Bruce Bartlett’s excellent panegyric to tax reform, The Benefit and the Burden, and First-Time Landlord: Your Guide to Renting out a Single-Family Home.  Clearly, we are on our way to fame and fortune.  I’ve already pegged Brad Pitt to play me in the movie.
Or maybe not.  Amazon’s rankings are updated hourly based on a secret proprietary formula.  Our exalted rank reflects the fact that a bunch of people ordered our book from Amazon recently.  By a bunch, I mean like a dozen.  This is a book about taxes, after all.  However, the books are now on back-order.  The last time this happened, our ranking quickly plummeted.
Numerous web pages and blogs speculate about what is in Amazon’s secret proprietary formula.  The consensus is that it is some function of current and historical sales.  Amazon also says this on their website, although somewhat obliquely.  Chad Orzel, who wrote How to Teach Physics to Your Dog showedthat there is a statistically significant negative correlation between Amazon’s sales rank and sales.  He knows this because he has actual data on sales (available from Amazon) and the sales rank, and he knows how to plot a regression line in Excel.  Orzel’s book is, in the author’s words, “moderately successful.” This is presumably because the book includes deeper insights than the negative correlation between rank and current sales.
Authors with technical skills have derived similarly deep insights.  For example, Ben Klemens, author of Math You Can’t Use, produced time series charts of the author rank for his book and several others.  Here is is hissummary of the process:
You can see from the plot that the pattern is a sudden jump and then a slow drift downward. The clearest explanation is that the sales rank is basically a function of last sale. When a copy sells, the book jumps to a high rank, and then gets knocked down one unit every time any lower-ranked book sells.
In other words, your author rank tends to increase when you sell a book and it falls when you don’t.  Brilliant!
But it apparently doesn’t always increase with a sale.  According to Amazon, “This can happen because the rank is a comparison of your book with all other books in the catalog. Your book may have been purchased recently, but if books in the rest of the catalog have recently been purchased more often than yours, your rank may remain constant or might drop.”
What we learn from this is that some authors apparently check their Amazon ranking when friends tell them that they have bought the book, and some are deeply disappointed.
Klemens did, however, find something interesting, which is that Oprah is apparently better for book sales than endorsement by the New York Times, at least back in 2006.
Several websites offer to track Amazon’s sales rank for authors, some for a fee. This is probably a bad investment as Amazon will provide all this information for free through its AuthorCentral website.
My author ranking has fallen to 12,843 while I wrote this.  Drat!  Quick, buy the book, and let me know so I can check my author rank.  And, Oprah, your viewers would love the book.
For more about Taxes in America, Howard Gleckman has a terrific review, “What to Read While Hanging out at the Fiscal Cliff.”  And Barnes and Noble has it in stock.  That won’t help my Amazon sales rank, but I’m okay with that.

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