An analysis of U.S. ISBN data by Bowker has revealed extraordinary growth for self-published books, 391,000 titles in 2012, which represents a 59% increase over 2011. Ebooks comprised 40% of ISBN numbers. Eight companies produced 80% of the print & e-book titles, including: CreateSpace, Smashwords, Lulu, Xibris (Div. of Author Solutions), AuthorHouse (Div. of Author Solutions), iUniverse (Div. of Author Solutions), Trafford (Div. Author Solutions) and WestBow Press (imprint of Author Solutions).
See full article "Bowker Self-Publishing Report: 2012." Market data is also available for download.