"But the projects which have proved most effective were those inspired by the German economist Silvio Gesell, who became finance minister in Gustav Landauer’s doomed Bavarian republic. He proposed that communities seeking to rescue themselves from economic collapse should issue their own currency. To discourage people from hoarding it, they should impose a fee (called demurrage), which had the same effect as negative interest. The back of each banknote would contain 12 boxes. For the note to remain valid, the owner had to buy a stamp every month and stick it in one of the boxes. It would be withdrawn from circulation after a year. Money of this kind is called stamp scrip: a privately-issued currency which becomes less valuable the longer you hold onto it."