Libertarians of the sort who like the works of Ayn Rand perennially use this hoary analogy: “The rising tide which lifts all boats.” It’s a catchy metaphor, vivid and easily visualized, but like many such convenient sayings it oversimplifies complex economic situations and can be used to justify malignant policies. The quote is from a 1963 speech by John F. Kennedy, but its current usage has morphed into a justification for conservative economic policies such as, “Don’t you dare tax the rich!”
Here are some variants from anonymous commenters at the Pharyngula blog:
A rising tide DOES raise all boats.
If you have a boat.
A rising tide may indeed lift all boats. But when roughly half the boats are permanently anchored on a short chain, that rising tide does nothing but submerge them.
Ooh! Let me play!
My variation is: A rising tide does nothing for a boat with a hole in it.
One need only envision a situation where it is only the rich who actually have boats – the rising tide analogy then works pretty well.