[Kitab]

I know basically nothing about economics, and even less about your game, but I have heard of a system called demurrage, advocated in particular by the finance theorist Silvio Gesell. It's basically negative interest. Instead of money gaining interest, it deteriorates, thus encouraging people to spend it as quickly as possible before it runs out! There was an experiment during the Great Depression, where a town in Austria introduced a new currency. Every month, the citizens had to pay to get a stamp to fix to their banknotes in order for them to stay valid: the stamps cost a certain percentage of the banknote's value. This was called an Umlaufsicherungsgebühr (fee-to-assure-circulation), and Silvio Gesell specifically talked about his system in terms of the velocity of money, if I recall correctly. The experiment in Austria was apparently very successful, and the inhabitants did funny things like paying their taxes early. I don't know how you'd implement this system in your game, but because it's digital, it sounds as though it would be quite simple.