Many MMOs allow players to choose sides or affinities. Sometimes, like in City of Heroes/Villains, players can choose between a clearly good or evil side. In other games, like World of Warcraft, the good/evil divide is a little less clear cut. Of course, these choices don't always revolve around good and evil. For example, they may involve choosing a race, or choosing between technology and nature. Here I'll present some data on different hypothetical choices that a game may ask a player to make when creating a character or during character development. What we'll see over and over again is that whenever a game asks players to make a choice, players seldom evenly distribute themselves. Instead, other factors, such as age, tend to be correlated with those choices. This in turn creates demographic differences between sides/affinities in games.

For example, let's start with the good and evil split. The graph below shows both an age and gender difference. Younger players prefer to be on the evil side, and this tendency decreases as age increases. There is also a relatively more mild gender difference in the mid-ranges where male players are more likely to be on the evil side than female players. What's interesting here is that the distribution roughly matches the 2:1 Alliance-to-Horde ratio in WoW.