Dreaming of Immortality in a Thatched Cottage - 1500s Exogenous/endogenous money , reflux , hot potato money , helicopter money , inelastic vs elastic currency. These are all part of the colourful lexicon developed by monetary economists over the centuries to outline a general set of problems: how does money get emitted from source, and when, if at all, does it return to source? We usually describe money as exogenous, hot potato, helicopter, or inelastic if it is emitted at the initiative of the issuer, and the issuer doesn't allow the public to exercise any initiative in returning this money back to source. Once it has been air-dropped into circulation from a helicopter, this kind of money becomes immortal, passing like a hot potato from person to person forever. We describe money as elastic or endogenous when the money-using public exercises its own initiative in both drawing money out from an issuing source and pushing (refluxing) this money back to the source. This sort of mo...