# Computing and Tracking the Amazon Sales Rank

The webpage http://www.novelrank.com/ provides a very neat simple way to track the sales rank of any book on Amazon. This service is completely free.

The sales rank is computed from the sales rate. The more a book sells per day, the lower the rank will be.  Here’s an approximate formula, taken from: http://www.edwardwrobertson.com/2013/02/a-quick-way-to-calculate-amazon-sales.html.

100,000 / rank = sales per day

So if a book is on rank 50,000, it sells about twice a day. As far as I know, a borrow counts as a sale and a free download as one third of a sale.

I use novelrank to track my ebooks. This is what the output looks like (launch of “Great Formulas Explained”):

Indeed a neat tool to see how a book is performing. Note that the tracking starts on the day you add it, dates before that are not shown.

As you can see, during the period when no sale is made the sales rank increases more or less linearly at about # 50,000 per day. The average rank during this time can be calculated by the formula: final minus initial rank divided by 2. When a sale is made, the rank makes a discontinuous jump to a lower value.

# Quantitative Analysis of Top 60 Kindle Romance Novels

I did a quantitative analysis of the current Top 60 Kindle Romance ebooks. Here are the results. First I’ll take a look at all price related data and conclusions.

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• Price over rank:

There seems to be no relation between price and rank. A linear fit confirmed this. The average price was 3.70 \$ with a standard deviation of 2.70 \$.

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• Price frequency count:

(Note that prices have been rounded up) About one third of all romance novels in the top 60 are offered for 1 \$. Roughly another third for 3 \$ or 4 \$.

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• Price per 100 pages over rank:

Again, no relation here. The average price per 100 pages was 1.24 \$ with a standard deviation of 0.86 \$.

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• Price per 100 pages frequency count:

About half of all novels in the top 60 have a price per 100 pages lower than 1.20 \$. Another third lies between 1.20 \$ and 1.60 \$.

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• Price per 100 pages over number of pages:

As I expected, the bigger the novel, the less you pay per page. Romance novels of about 200 pages cost 1.50 \$ per 100 pages, while at 400 pages the price drops to about 1 \$ per 100 pages. The decline is statistically significant, however there’s a lot of variation.

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• Review count:

A little less than one half of the top novels have less than 50 reviews. About 40 % have between 50 and 150 reviews. Note that some of the remaining 10 % more than 600 reviews (not included in the graph).

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• Rating over rank:

There’s practically no dependence of rank on rating among the top 60 novels. However, all have a rating of 3.5 stars or higher, most of them (95 %) 4 stars or higher.

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• Pages over ranking:

There’s no relation between number of pages and rank. A linear fit confirmed this. The average number of pages was 316 with a standard deviation of 107.

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• Pages count:

About 70 % of the analyzed novels have between 200 and 400 pages. 12 % are below and 18 % above this range.