@Carolyn-and-Kerry0 The Overall rating isn't an amalgam or average of the other ratings- it's a separate rating completely. It's puzzling why guests do this, and it drives hosts crazy. It could be because there was something the guest thought could use improvement that doesn't fall under any of the other ratings, but most often I think it's just that the guest thinks 5*s should only be given to some luxury resort or they just never give 5* on some kind of principal. And Airbnb tells guests that 4*s is a Good rating, so it's not like they're trying to harm your ratings- if they wanted to do that, they'd be rating 2 or 3*s.