One in four Kindle ebook sales were for self-published writers in 2012, according to data revealed at a trade presentation by Amazon.
The online retailer presented the stats at a trade presentation, during which it said that 25 of the top 100 books sold via Amazon.com were uploaded by indie authors via the Kindle Direct Publishing (KDP) platform.
Writer.ly, a web platform linking authors with freelance editors, designers and marketers, posted a picture from the presentation on Twitter, and Amazon later confirmed the stats.
A spokeswoman said: "This figure is referring to Kindle books on Amazon.com in 2012, with 'indie' meaning books self-published via KDP. So a quarter of the top 100 bestselling Kindle books on Amazon.com in 2012 were self-published via KDP."
While the figures were for Amazon's US marketplace, and date from last year, industry figures believe the UK is not far behind in the trend.
Orna Ross, director of the UK Alliance of Independent Authors, told the Guardian: "If the UK isn't quite there yet then it's just a time lag - we are seeing that more and more of the top books around the world are published by authors themselves.
"We are in the middle of a major change. I wouldn't be at all surprised if we reached a situation where the majority of the top books are author-published. I don't see what would stop that."
Hugh Howey, who was a KDP author before being picked up by Random House, becoming a bestseller, tweeted: "Taken together, indie authors form a new major publisher to round out the "Big 6." That's the level of sales we represent."
Howey has previously spoken of his desire for Amaozn to publish data about its mid-list KDP authors, rather than just breakout successes, to demonstrate the median sales which can be achieved through the platform.