I asked her for her phone number, she gave me an estimate

From The Science of Liberty: Democracy, Reason, and the Laws of Nature by Timothy Ferris.

For an allegedly dismal science, economics generates lots of jokes. Economists, it is said, are frequently wrong (they "forecast twelve of the past three recessions"), tend to be noncommittal ("If you laid all the world's economists end-to-end, they would not reach a conclusion") and like to hedge their bets ("I asked an economist for her phone number and she gave me an estimate"). Harry Truman wanted a one-armed economics advisor who wouldn't keep saying, "On the other hand." Ronald Reagan speculated that if economists had invented Trivial Pursuit, the game would have a hundred questions and three thousand answers. As early as 1855, Walter Bagehot of the Economist was claiming that "no real English gentleman, in his secret soul, was ever sorry for the death of a political economist."