The Adventures of an Independent Author: Self-Publishing Statistics
Interesting stats from this blog:
10% of authors earn 75% of royalties
Total Books published by country, the top three are : USA, UK, France
56% make over 25k, 28% over 50k, 15% over 100k
Two types of author: 56 % : Sell book cheaply to get more readers. 44% : Charge a higher price and make more money from fewer readers.
42% of authors can never changed the price of their books
41% Paid for a cover designer (the most popular form of paid help) 29 % paid for copy editing.