Although it comes with a number of caveats, Bowker's newest report on the number of self-published titles rose again in 2013, increasing 16.5%, to 458,564. The increase was due entirely to the release of new print books which rose 28.8% to 302,622 offsetting a decline in self-published e-books which fell 1.6%, to 155,942.

The totals are based on self-published titles that have an ISBN registered with Bowker as of August 6, 2014 with the year referring to the year of publication provided by the publisher. The report also does not include titles published through Kindle Direct Publishing since books created there do not need an ISBN, and also does not include titles from Nook Press. In addition, it is likely some titles are double counted as self-published authors who do both print and e-books often give different ISBNs to the same title. Beat Barblan, Bowker director of identifier services, explains that the counts are ISBNs, not titles, “and indicate trends rather than absolutes. We’re consistent in the way we calculate this each year, making the reports accurate reflections of trends.”

The report, Barblan continued, shows a self-published market that is maturing into a serious business. He pointed to an 8% increase in the number of ISBNs registered by small publishers--publishers that registered fewer than 10 ISBNs--as evidence of a move by self-publishers to business--owner rather than writer only.

Small publishers registered 46,654 ISBNs in 2013, placing that group fourth among companies that registered ISBNs. The Big Three in 2013 were Amazon’s CreateSpace which registered 186,926 ISBNs last year, followed by Smashwords which registered 85,500 ISBNs and Lulu which had 74,787 ISBNs. The different Author Solutions divisions had 44,574 ISBNs. The CreateSpace figure reflects only print ISBNs, while Smashwords includes only registered e-books.