A virtual economy most often used in MUDs and similar multi-player games. The basic concept is to keep the amount of currency in the system constant. For every source (faucet) in the economy, there is a drain. Idealy the amount of currency entering into the system equals the amount leaving by way of the drains.

One example of a working version of this economy can be found at Core 2650. In this MUD, the source of currency is from mining. Wear and tear on equipment, use of energy, taxes/fees are examples of the drains in the economy.