I also observe that the number of ratings come and go. Rating number increase and decreases again. My guess was that ratings are deleted when a user uninstalls the app, but this is not the case, right? Why do 5-star ratings continuously disappear? I find it unfair that bad ratings, that are several years old, have the same weight as if they were given yesterday. Google Play has a different system: The app rating is not the overall rating but is based on a period of the last months (not clearly specified). This is much more fair and informative as it respects the current and not the initial quality of the app!