First, Assume a Ladder

I was reminded of a joke I haven't heard in a long time but that everyone should keep in mind when listening to economists prattle on about their theories.  I have heard of few variants, but the one from this health care blog was the first to show up in Google and will do just fine:

[Have you heard ]the story of the engineer and the economist who, walking through a remote forest, fell into a very deep hole with vertical sides[?]  The engineer said, "We'll die down here.  No one can hear us calling for help, and it is impossible to climb out."

 The economist said, "On the contrary, there is no problem.  First, assume a ladder."