While this isn't an entirely unexpected development, it’s definitely a new change -- one that we caught because we are constantly monitoring App Store positioning and visibility. After some in-depth (and still ongoing) analysis by our Performance Labs team, we can conclude that Apple is testing changes to the iTunes ranking algorithm.
Fiksu notes that previously download volume and velocity of downloads affected app rankings. Now there are two key additions developers should be aware of.
1) Ratings now affect rank, in addition to downloads
2) App store positioning now updates every 3 hours instead of every 15 minutes
As evidenced by the graph below, apps with ratings of 4 or more stars received a rank boost in late July and have maintained that rank throughout August. Poorly rated apps with less than 3 stars received the opposite treatment about two weeks later, dropping off precipitously in rank and staying that way. Average rated apps, between 3 and 4 stars, suffered a slight degradation in rank but have generally been less affected.
Check out the chart below or hit the link for more details...
Read More [via 9to5Mac]