One common purpose of combining two things into a single bucket is to create an impression that these two things are closely associated. It's an extremely common practise amongst PR people. But Dave is presumably a DBA not a PR hack so I don't imagine his purpose of doing it was that. Probably it was just a rather silly (because it might cause people to think that he was trying to create associations between disagreeing with him and whining and between agreeing with him and being educational) means of reducing the number of buckets. Anyway, his arithmetic is wrong, since the educational posts are mostly negative and should be in both buckets so that the percentages should sum to more than 100%, but he has them sum to 100%. When wearing my mathematician hat I used to hate it when people got careless like that with numerical data, but these days I no longer worry about it, just point it out when it seems appropriate to do so.