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This article was written by the god Dentin, originally posted on July 03, 2009. Updated July 17, 2009. (original version)

Gold Balancing in MMOs

All too often, articles talking about gold balance or economies do little more than state that 'most MMOs have problems with their economy'. Instead, I'll describe how Alter Aeon has successfully managed its gold economy.

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 desirable. Nevertheless, it handles its gold economy fairly well, and the guiding principles for its economy are applicable to much larger games.

Before the gold economy can be automatically managed a foundation of accurate gold tracking statistics are needed. In addition to simply tracking sources and sinks, logging of large or otherwise unusual transactions should be performed. Some of the data available to the Alter Aeon game server are:

  • Tracking for all gold sources and sinks

  • Real-time/live gold statistics

  • Logging for unexpected or 'dangerous' gold changes

  • Large gold changes, even valid transactions, trigger sanity check warnings

  • A single global value representing all gold in circulation

Tracking the flow of gold through the system is critical, and without this data it's very difficult to properly manage an economy (though you may be surprised at how many small games try anyway.) Sanity checks and logging of dangerous transactions are not directly used for economic control, and are intended to give the administration insight into the types of transactions that occur and help monitor for exploits.

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 creation is calculated from statistics and game parameters. However, this alone is still insufficient to stabilize the economy. In the long run, gold creation and destruction has to be managed at a global scale, to prevent unlimited hoards from accumulating and to force the sources and sinks to balance.

After much experimentation, we ended up with several layers that each contribute to the whole system:

  • In Alter Aeon, mob death, theft, treasures and quests each contribute to new gold in the game. To prevent any one of these means of obtaining gold from becoming the dominant source of "easy money", the game tracks and dynamically adjusts gold creation for each source. Sources that contribute disproportionately to the total influx are automatically scaled back.

  • Stored gold on inactive or infrequently active players can create a problem, in that the stored gold is effectively removed from circulation. So that new and active players have means to obtain gold, and to prevent packrats from accumulating unlimited hoards, large quantities of stored 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.

  • Clan and guild bank accounts can only hold a limited quantity of gold. Since maintaining a clan requires dues to be deposited (gold destruction) the limit for clan gold storage is fairly high (on the order of 50 million.)

  • Dynamic pricing of items alters the price of items for sale in shops based on how often the items are bought or 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.

All these things are good, but still not quite enough. To help hold it all together, there needs to be a global control system. So that's exactly what we built for Alter Aeon.

The most critical part of this implementation is called the global offset controller. The global offset controller monitors the total quantity of gold in existence, and subtly tweaks the gold sources based on that value. There are two parts to this controller, 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 controller looks at recent deviations from the long term expectation, and aggressively modifies the global gold sources. This controller 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 controller 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 result is a system that allows for substantial deviations in the short term allowing for rewarding game play, 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 all or nearly all gold creation.

  • 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.

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