[slipperyp]

"biased" how? That simply means that for the more recent data set, the owners bothered to decypher a small set of user agents (those represented in the graph - latest verions of dominant browsers), everything else is marked "other" and it shows that in Jan 2014, ~20% or fewer of clients were connecting from anything but some latest-version browser (and of whatever resources this covers, Chrome is by far the leader). That doesn't strike me as bias - just data simplification.