I first heard the best joke about economics in 1975. The teller was the nuclear physicist (and nuclear power advocate) Sir Phillip Baxter, and he told it in answer to a question I had asked at a public forum.
The joke is:
A physicist, a chemist and an economist are shipwrecked on a desert isle, along with a container full of cans of baked beans.
The chemist says that if they can start a fire, he can calculate the temperature at which a can will explode.