Indie authors often find success in the digital publishing arena but how many titles do they actually sell? Unlike the traditional publishing industry the average self-published title does not have an ISBN number. This number serves as your online SIN and because most e-books do not have this number, it is impossible to quantify meaningful sales data.
ISBN numbers are critically important for an author to claim ownership of their work and support the self-publishing movement. Over the course of 2014, 30% of all e-books being purchased in the U.S. do not use ISBN numbers and are basically invisible to the industry's official market surveys and reports; all the ISBN-based estimates of market share reported by Bowker, AAP, BISG, and Nielsen are totally incorrect.