Recently, a large corporation hired several cannibals to increase their diversity...
... "You are all part of our team now," said the Human Resources rep during the welcoming briefing. "You get all the usual benefits and you can go to the cafeteria for something to eat, but please don't eat any employees."
The cannibals promised they would not.
Four weeks later their boss remarked, "You're all working very hard and I'm satisfied with your work. We have noticed a marked increase in the whole company's performance. However, one of our secretaries has disappeared. Do any of you know what happened to her?"
The cannibals all shook their heads, "No."
After the boss had left, the leader of the cannibals said to the others, "Which one of you idiots ate the secretary?" A hand rose hesitantly. "You fool!" the leader continued. "For four weeks we've been eating managers and no one noticed anything. But now, you had to go and eat someone who actually does something.”