The Author Earnings website has worked hard at 'scraping' data from Amazon's various sites to provide unprecedented detail on sales data. As Amazon now represents close to a majority of print titles sold, knowing what is being sold and by whom is very interesting indeed. The data shows that independent authors represent a large and rapidly growing fraction of book sales on Amazon. There is also ample evidence that having a book listed on the Amazon bestseller lists provides a substantial boost to non-listed titles from the same author. Overall, Author Earnings claim that they identified over 9,000 authors earning more than USD $10,000 per year, and half of that number were earning over USD $20,000 per year. Read the whole report, which goes into much greater detail.