Sorry if I did miss this, but that sounds interesting (and not little controversial):
Starting in July, authors of the Kindle Direct Publishing program are going to be paid based on how many pages people read—not how many pages are downloaded, but how many pages are displayed on the screen long enough to be parsed. This per-page model applies to books published through Amazon that are read as part of the Kindle Unlimited and the Kindle Online Lending Library programs.
Source:
https://kdp.amazon.com/help?topicId=A156OS90J7RDN via
http://www.theatlantic.com/business/...riting/396269/