At the risk of incurring much wrath, I have known a teacher (a friend) who did not work very hard 9 months out of the year, and then didn't work at all the other three months. I also have a friend, a teacher, who spends significant time not merely grading papers, but improving her curricula, knowledge, and teaching skills. She does so 9 months out of the year. I am not trying to belittle the work that teachers do, but there is a significant amount of time that many teachers are not working. I would assume that is a significant reason for the dot's location on the graph.