on average. From the Wall Street Journal http://online.wsj.com/news/articles/SB10001424052702303640604579298604044404682
i believe amazon's formula for determining sales rankings has been disputed as not being entirely reliable...
How about Barnes and Noble then, in which 24% of Nook Book sales every month is self-pub? http://www.barnesandnobleinc.com/press_releases/04_09_13_nook_press_release.html * PubIt! continues to attract 20% more independent authors every quarter. * Titles from self-published authors continue to increase by 24% each quarter in the NOOK Store™. *Customer demand for great independent content continues to dramatically increase as 30% of NOOK customers purchase self-published content each month, representing 25% of NOOK Book™ sales every month.
Those are actually a different subject though - number of authors versus sales (unless you meant sales for the NOOK store). Are there figures available for past years? I've seen people on other forums mention several numbers (without cites, unfortunately) which offer contradicting increases/decreases in percentages. It wouldn't surprise me to see a gradual increase, as more and more "bandwagon" writers drop out and the more "professional" writers gain publishing experience/reputations.
I was referring to the 25% of Nook ebooks sales each month is from self-published ebooks. Customer demand for great independent content continues to dramatically increase as 30% of NOOK customers purchase self-published content each month, representing 25% of NOOK Book™ sales every month. If it's at 25% at Nook, it's very likely to be higher at Amazon. 32% at Kindle might sound about right.
