" Any more than four ratings gives a false sense of precision. Too many ratings make managers feel they should be able to achieve a level of granularity in their assessment of people’s performance that isn’t actually possible. Also, when managers have too many ratings at their disposal they tend to try to show an uptick every review to make the person “feel” like they are improving "

― Kim Malone Scott , Radical Candor: Be a Kickass Boss Without Losing Your Humanity