Looking at the percentage of authors making more than $500 a year is misleading. It's never been easier to publish a book, so the pool of marginal books will grow. This doesn't necessarily reflect the prospects for serious authors.

I'm a self published author. I make around $10,000 a year from print sales. My books started as experiments. I already had e-books. I decided to turn two manuscripts into print books.

I spent about $500 and two weeks on formatting and design. I didn't copy-edit beyond what I had done myself. And I waited to see if it sold.

It did, so I turned more e-books into print books, and made new books aimed at print.

But if the books hadn't sold, I would be classed as one of the poor authors making less than $500 a year. But that would be a misleading data point, because my initial foray was rather tentative.