Ten finance guys are drinking in a bar. Nine of them are Masters of the Universe — wheeler-dealers who make many millions of dollars every year. The tenth is what Gordon Gekko, in the movie “Wall Street,” called a “$400,000-a-year working Wall Street stiff.”
Then the stiff leaves for a while, maybe to answer a call of nature. When he leaves, the average income of the guys still in the bar shoots up, because he’s no longer dragging that average down; when he comes back, the average drops again. But these fluctuations in the average don’t reflect changes in anyone’s income.