Gary McLaren wrote in http://www.publishyourownebooks.com
“The Association of American Publishers (AAP) is reporting today that e-book sales grew by an estimated 117.3% for the year of 2011. For the US publishing companies who report revenue to AAP, e-books (excluding the religious category which is tracked separately) generated revenue of $969.9 million during 2011 compared to $446.3 million in 2010.
2011 was not such a good year for print books however. Adult trade hardcover ($1,293.2m) and paperback ($1,165.6m) fell 17.5% and 15.6% respectively.
E-books have now grown by more than 100% for three consecutive years.
Keep in mind that this data relates to the US market and only reflects those publishers who report sales data to Association of American Publishers. The e-book market is considerably larger than that when all of the smaller and independent publishers are taken into account, and especially if all countries were included in one report.
With such exponential growth it is difficult in the graph above to see the values of e-book sales in the earlier years of 2002 through 2005. Another chart shows e-book revenue growth as reported to AAP for the past 10 years.”