Alter Aeon is a MUD and is relatively small compared to the heavyweight MMOs (WoW for example), but it is still large enough that manual adjustment of the economy isn't really feasible. Nevertheless, it handles its gold economy fairly well, and the guiding principles for its economy are applicable to much larger games. This is the economic system I'll be describing.
The foundation of Alter Aeon's economic stability is accurate gold tracking:
- All gold sources and sinks are tracked and understood
- Real-time gold stats are available
- Unexpected or 'dangerous' gold changes are logged
- Large gold changes, even valid transactions, trigger sanity check warnings
- There's a single global value representing all gold in circulation
Once statistics are available, a lot of games handle their economy by having active admins manually adjust parts of the system periodically. For larger games, this becomes virtually impossible; further, we decided that this would be a complete waste of valuable admin time. We have computers to do boring tasks like this.
Therefore, we don't bring admins or builders into the picture at all. Nearly all gold drops are calculated from statistics and game parameters. Adding this helped tremendously, but was still not enough to stabilize the economy on its own. In the long run, we ended up with several layers that each contribute to the whole system:
- Mobs drop gold based on their death or theft rates; object gold is also based
on the looting rates of treasure objects. The purpose of this dynamic feedback is
to prevent one source from dominating or becoming the 'easy gold'.
- Large quantities of gold are taxed. Characters holding more than a million gold
are taxed on the amount above a million gold, to the tune of about 2% per week. The
purpose of the tax is to prevent packrats from accumulating unlimited hoards.
- Clan and guild bank accounts can only hold a limited amount. Since the very existence
of the clan indicates that gold is being paid in dues, this limited amount is fairly
high (on the order of 50 million gold.)
- Player shops can hold an unlimited amount, but generally shops have high rent rates,
so gold turnover has so far not been a problem there.
- Dynamic pricing of items alters the price of items for sale in shops based on how
often they are shoplifted. If a particular item is stolen too often, the price is
lowered and the theft difficulty is raised to make the price more cost-competitive.
This most critical part of the system is called the global offset controller. This control system monitors the total quantity of gold in existence, and subtly tweaks the gold sources based on that value. There are two parts to this control system, one being the short-delay controller which manages quick transients (on the order of a week or two), while the long-delay controller manages trends.
The short-delay term of the control system looks at local deviations from the long term expectation, and fairly aggressively modifies the global gold sources. This short-delay term can change total gold influx on the order of 50% in a one week period if necessary.
As the total quantity of gold in existence changes, the long-delay term of the control system slowly adjusts the set point for the short-delay calculations. If a large amount of gold is in circulation, the short-delay set point will be lowered, globally lowering the input of gold into the system.
The final combination of all these things is a system that allows for fairly substantial deviations in the short term, but always returns to long term stability. Total gold in circulation has varied by less than 10% over the last two years, and gold in Alter Aeon has once again returned to its rightful place as a valuable trading commodity.
In conclusion, here is a short list of important things we learned:
- All sources and sinks should be tracked.
- Autocalculate gold drops on everything you can.
- Adjust specific types of gold drop based on usage.
- Limit gold hoarding. Inflation is one way to do this, taxes are another.
- Use global controllers with feedback for long term stability.