I have a big problem

Bill and Boris are taking a break from a long summit. Boris says to Bill, "Bill, you know, I have a big problem. I don't know what to do about it. I have a hundred bodyguards and one of them is a traitor. I don't know which one." "Not a big deal Boris, I'm stuck with a hundred economists I have to listen to all the time before any policy decision, and only one tells the truth but it's never the same one."