In Part I, MMO developer Brian Green points out that a realistic economic simulation in a MMO may not actually be possible or even fun for the players. In Part II, he explains how to create a game economy that maximizes fun.
To discuss economic adjustments, we need to have a design for the economy. The traditional and perhaps simplest design for a game economy is called "faucets and drains". In this design, you have sources of income (the faucets) and ways that income can be spent to the game (the drains). Typical faucets include rewards from quests or missions and items of value acquired from defeated enemies. Drains include consumables that must be used in the game, customization options, and taxes such as auction house fees, equipment repairs, etc. Note that faucets only include the situations where the game creates money, and drains only include the situations where the system takes money out of the system.
In the theoretically ideal economy, the faucets and drains should be equal. A player should be spending money as fast as they make it to prevent inflation. However, this isn't terribly fun as we mentioned before. Players want to make a bit more money than they spend, so that they can have a feeling of mastery over or helpfulness in the game. So, ideally, you should deal with a bit of inflation but should avoid hyperinflation, or the rapid increase in money leading to the value of each unit of currency decreasing significantly.
How can a designer balance the economy to maximize fun? It's important to include the proper tools to observe and adjust the economy. Metrics to show the velocity of goods and currency in your game are good to have. Even simply knowing how much money the top earners in your game have in order to track changes from day to day can help give a feel for how the economy is working on a practical level. Your game should then have tools to adjust the economic factors based on your measurements. Being able to increase or decrease randomized rewards, such as the valuable items and currency obtained from defeating an enemy, is important. Adjusting the prices that NPC charge for basic commodities is also useful, especially if you need to give newer players the ability to catch up to more established players. Another tactic is to introduce special deals in the game world for a short period of time; having a special auction of rare items for in-game currency can help reduce some of the excess money in the world. Finally, use your metrics to help notice potential bugs, such as the ability to duplicate money or abuse an NPC's faulty buying or selling routines to earn easy cash. A sudden increase in money supply can indicate the presence of such bugs.
What about the economy that happens between players such as posting goods on the auction hall, crafting, and the like? It's important to remember that a player buying an item at auction isn't really spending the money in terms of the economy, the money is just being transferred from one player to another. Except for taxes such as a fee for posting and/or selling goods, buying an item from an auction isn't a drain in terms of the game economy. However, the game economy and the level of inflation can affect the player to player economy. Players with more money, such as experienced players creating alternate characters ("alts"), will be able to offer more money for similar items compared to a player with less money.
A major component of the player to player economy is usually crafting, or the creation of usable goods from raw materials gathered by the player. This encourages some economic activity as players collect the raw materials and sell those to other players, then as the crafters create the finished product and sell that to others. In general, a game designer won't have to worry too much about this system since players will tend to find an equilibrium point for prices based on the state of the economy. The biggest game design challenge is to limit the creation of raw materials if limits on the number of craftable items; this is similar to limiting the amount of items obtained from other sources that players may want to sell to each other. The second major issue to consider is how fun crafting is. Most players expect a crafting profession that they have invested time into to be useful and even profitable for them. For example, if they have to create 100 level 1 items to get access to level 2 items, they will expect an NPC to buy those level 1 items for some amount of money, for at least as much as the fixed costs of vendor-purchased materials. Making players craft at a loss of income will make crafting unattractive and unfun in a game.
In conclusion, a designer needs to make the game economy fun. Adding controls to the game economy allows the designer some control over the money supply to adjust inflationary pressures. The game economy affects the player to player economy, but a designer has significantly less control over this; on the other hand, players tend to adjust this economy themselves since it usually operates outside of the game system. The biggest issue a designer has to worry about in a player economy is adjusting how often a player can acquire something that others may want to buy. Ultimately, a simulation may be more realistic, but it might not be more fun for the players. Sometimes you just gotta fake it.
Brian Green, known by the pseudonym Psychochild, is an experienced MMO developer. He's best known as the former developer of the classic online MMO Meridian 59 and as the writer for his professional blog.