A new report issued by Bowker found that a total of 786,935 ISBNs were issued to self-published authors in 2016, an 8.2% increase over 2015.

According to the report, ISBNs for print books rose 11.3% to 638,624 titles, while e-book ISBNs for self-publishers fell 3.2% to 148,311. Since Bowker measures the number of self-published books by ISBN, its count does not include e-books released by authors through Amazon's KDP program, as they use ASIN identifiers rather than an ISBNs.

The 11% increase in print self-published titles was a slower gain than the 34% increase in 2015 over 2014. While the number of self-published e-books did fall in 2016, the decline was slower than the 11% drop reported in 2015.

"Overall, we believe that these numbers point toward an ongoing maturation and stabilization of the self-publishing industry," said Beat Barblan, director of identifier services at Bowker.

Amazon's CreateSpace was by far the largest publisher of self-published print books, releasing 501,043 titles. The output marked an increase of 18.2% over 2015. Lulu was second, publishing 41,907 titles in the year, a decline of 5.1%. Coming in third was Blurb, which released 21,365 self-published titles last year. Author Solutions released 19,270 self-published print titles (through multiple imprints) last year, for a decline of 6.4%.

On the e-book side, Smashwords accounted for the highest number of titles, releasing 89,041, down 8.2% from 2015. Lulu was in second place with 33,336 titles, a 5.2% decline. The Author Solutions imprints released 11,018 e-books, a jump of 175%. The Author Solutions increase reflected a rebound in the number of e-books published; in 2015 they did 8,634 e-books and in 2012 published 18,846.

Bowker noted that since 2011 the number of ISBNs from self-publishers has jumped by 218%, from 247,210 to 786,935.