Digital Book World E-Book Best-Seller List Methodology
When we decided to build our new Digital Book World E-Book Best-Seller List, we wanted to give people a better view into what is actually happening in the e-book marketplace than they already had.
In the absence of real-time, raw sales numbers for all the retailers — which nobody has — we thought it best to address some of the problems with current e-book best-seller lists:
— One-hit wonders
— No differentiation between $0.99 e-books and $12.99 e-books
— No accounting for which publishers are selling the most e-books
In response, our list measures sales ranking over a week’s time to reward books that are best-seller lists every day of a week versus just one day. We also show price and have created four separate lists that organize all the books into price categories. And we show the publisher, so the industry can keep track of which publishers are selling the most e-books and how they’re doing it.
Below is basically what we do every week. Unfortunately, we won’t be exposing our full methodology as we don’t want to give everything away but the below should be telling. Readers should also know that certain industry experts outside of Digital Book World and Iobyte Solutions (my company, which is powering the raw data behind list) have taken a look under the hood, so to speak, and help influence our methods.
Those experts are listed in the press release.
Our basic methodology:
1) Best-seller rank observed from the six top retailers (Kindle, Apple, Nook, Google, Kobo, Sony)
2) Lists observed for seven consecutive days (Sun. – Sat.)*
3) Each appearance on a list gets an unweighted score based on the ranking
4) Ranking scores are logarithmically determined (i.e. top scores are much more valuable than lower scores)
5) Each retailer weighted by approximate market share as determined by the editors of Digital Book World and Iobyte Solutions
6) Additional appearance credit is awarded for appearing on multiple lists
7) Combined scores for the week determine final score for each title
8) Titles are ranked by final scores and also grouped into sub-lists by price (four separate price-band lists: $0 – $2.99; $3.00 – $7.99; $8.00 – $9.99; and $10.00 and above)
9) Minimum price that appeared at any point during the week on any retailer is used for determine price band (assumption that low price is an important driver of ranking)
Let us know your thoughts: Leave a comment below.
* Note. This has been changed as of the week of 2/3. See editorial note here.