Two economists walking down a road see a twenty dollar bill laying on the side-walk.

The first economist asks "is that a twenty dollar bill?" The second economist answers "It can't be, because someone would have picked it up already."

They keep walking.

Further down the road they see a pile of trash. One economist says to the other: "I will pay you $1000 to eat it".

The second economist agrees to eat the trash, finds it disgusting, and says "I will pay you $1000 to eat this other pile of trash".

The first economist agrees and eats it.

Upon reflection, the first economist says to the second: "We both just ate trash, and neither of us is better off for it..."

The second says to the first - "Look on the bright side: we raised GDP by $2000."