There's a very useful analysis of self-publishing via the POD route on the Writer Beware website. While this extract discusses sales statistics, the complete article is far more extensive and essential reading for everyone who is considering self-publishing their work.
Despite some highly publicized successes, the average book from a POD service sells fewer than 200 copies--mostly to the authors and to "pocket" markets surrounding them--friends, family, local retailers who can be persuaded to place an order. According to the chief executive of POD service iUniverse, quoted in the New York Times in 2004, 40% of iUniverse's books are sold directly to authors.
POD services' own statistics support these low sales figures. AuthorHouse's online Fact Sheet, updated in September 2008, reported 36,823 authors and 45,993 titles. According to the New York Times, AuthorHouse reports selling more than 2.5 million books in 2008, which sounds like a lot, but averages out to around 54 sales per title.
iUniverse's most recent Facts and Figures sheet reports that the company published 22,265 titles through 2005, with sales of 3.7 million: an average of 166 sales per title. Obviously some titles can boast better sales (Amy Fisher's If I Knew Then sold over 32,000 copies)--but not many. According to a 2004 article in Publishers Weekly, only 83 of more than 18,000 iUniverse titles published during that year sold at least 500 copies. And in a 2008 article in The New York Times, iUniverse's VP, Susan Driscoll, admitted that most iUniverse authors sell fewer than 200 books.
As of 2004, stats for Xlibris were similar. According to a Wall Street Journal article, 85% of its books had sold fewer than 200 copies, and only around 3%--or 352 in all--had sold more than 500 copies. Things looked up in 2007: according to Xlibris's own internal reports, recently obtained by Writer Beware, 4% of its titles had sold more than 1,000 copies. However, the averages still aren't good. As of mid-2007, Xlibris had 23,000 authors and had published 23,500 titles, with total sales of over 3 million--around 127 sales per title.
Once independent companies, AuthorHouse, iUniverse, and Xlibris are now all owned by the same company, Author Solutions. In a New York Times article published in early 2009, Kevin Weiss, Author Solutions' CEO, put the average sales of titles from any of the company's brands at around 150.
Lulu.com, one of the most popular and cost-effective of the POD services and still independent despite the apparent trend toward consolidation among POD services, is explicit about its long tail business model. In a 2006 article in the Times UK, its founder identified the company's goal: "...to have a million authors selling 100 copies each, rather than 100 authors selling a million copies each." A Lulu bestseller is a book that sells 500 copies. There haven't been many of them.
Many thanks to Victoria Strauss for giving me permission to use this piece.