Amazon-owned audiobook retailer Audible is lowering the royalty rates it pays authors who self-publish their audiobooks through the website.

As first reported by Gigaom, Amazon announced the news on a blog post on its ACX website. ACX, or Audiobook Common Exchange, is the company's platform through which authors can post their available audio rights and producers can then bid on the rights, to create the work. Creators then have the option to sell the audiobooks exclusively through Amazon, Audible and iTunes at a higher royalty rate, or through a wider ranger of retailers, at a lower rate. Up until now, Amazon was offering an escalating rate of 50%-90% on ACX titles sold exclusively; now it is dropping the rate to a non-escalating 40%. (ACX audbiobooks distributed non-exclusively are dropping to a non-escalating rate of 25%.)

The move, Amazon said in the post, which takes effect March 12, 2014, will, in part, encourage authors to become more aggressive marketers. With the drop in royalty rate, for authors selling their audiobooks exclusively, Amazon has bumped up its "bounty" program. The bounty is the amount awarded to the author (or royalty earner) whenever an audiobook is the first purchase of a new member of the program. Previously the bounty was $25, and now it is $50.

Audiobooks signed up before March 12, and those currently selling under the existing royalty structure, will continue to draw the original rates.