The number of books self-published in the U.S. saw more rapid growth in 2018, jumping 40% over 2017, according to Bowker’s annual survey of the self-publishing market. In its report, “Self-Publishing in the United States, 2013-2018: Print and E-books,” the total number of print and e-books that were self-published in 2018 was 1.68 million, up from 1.19 million in 2017. Bowker measures the size of the market based on the number ISBN’s registered and thus does not include self-published e-books by Amazon’s Kindle division, which uses an Amazon identifier.

Amazon is considered to be largest publisher of self-published e-books, even if no number is available. Amazon’s CreateSpace division dominates the print self-publishing market, with 1.4 million self-published print titles last year, up from 929.290 in 2017. Lulu published the second most print self-published titles last year, with its output rising to 37,456 titles, from 36,651 in 2017, according to Bowker. Author Solutions, through its many different imprints, released 16,019 print self-published print books last year and 10,585 e-books, with both figures slightly higher in 2018 over 2017.

Excluding Amazon, the top e-book self-publisher last year was Smashwords, which released nearly 72,000 titles, down 3% from 2017. Lulu was in second place on the e-book self-publishing list, with 30,021 titles, down from 30,747 in 2017.

Beat Barblan, v-p of publishing and data services at Bowker and chairman of the International ISBN Agency, said the self-publishing business seems poised to continue to post solid gains. “As more authors take advantage of the abundant tools now available to publish, distribute, and market their own books, we expect that self-publishing will continue to grow at a steady pace,” Barblan said.