Here's a complete list:
https://amazonpublishing.amazon.com/our-imprints.htmlWe know Amazon has been doing what it can to push imprints. Amazon Charts was really about that, at least in part. Imprint books are boycotted by most sales outlets, so no way they can make a traditional bestseller list no matter how much they sell. Charts is a way of rewarding imprint books that do well. We've also heard about changes in the search algorithms intended to boost Amazon product lines. What else may be happening is, as RPatton says, hard to say.
For what it's worth, my prawny numbers are about what I'd expect. They're mostly down, but I haven't had a sale since October 26, and only 12 pages read in that time. With those kinds of figures, I'd expect my numbers to have descended more than they have.
While anything is possible, I have a hard time thinking Amazon is adjusting the ranks of KU books downward. If people get no ranking boost for being in KU, unless they continue to rake in huge amounts of money, why be in KU? It would be a bold move to combat scammers, but there are a lot of honest people in KU who might just bail out, so it would seem contrary to Amazon's interest to make a move like that.
As indies, we have a habit of succumbing to chickenlittleism. There are times when the sky actually isn't falling. As some of you have said, I think technical issues, possible exacerbated by big pushes by Amazon and the trads, are to blame. If the trend persists, then it may be a different story.
Remember when a 50% royalty option showed by briefly on the dashboard, and many, many people were convinced Amazon was getting ready to cut royalties? I thought at the time it was an accidental inclusion of the Amazon imprint ebook royalty rate in the chart. Amazon said it was a mistake. Royalties haven't fallen to 50%. Sometimes a mistake is a mistake.
It would be nice if we had more stable working conditions, particularly for those of you who depend on your writing income. (At that point, it becomes natural to freak out.) However, we've gone through self-proclaimed Armageddons many times and are still here. Take slow, deep breaths and wait until more information is available before worrying too much.