The Importance of Knowing Your Key Variables

"I was lucky I had a sensational teacher in Ben Graham," says Charlie Munger. "A smart man playing his own game and working at fooling you could do a pretty good job of it" If something is not very predictable, forget it: You don't have to be right about every company,. But then when you find one where you really do know the key variables, which ones are important,you've got to fix on them."