Once upon a time when I was a UPS driver the Center Manager was ranting about absenteeism at an AM meeting. After the meeting I went up to him and said “I bet 40% of the absenteeism around here is on Mondays and Fridays.” He said “Yeah, it probably is!” I said “Of course, that is 40% of the work week.” He got a thoughtful look on his face and after a moment said sheepishly “Yeah, I guess that’s right.”