We analyze a unique data set from a massively-multiplayer online video game economy called The Kingdom of Loathing to assess the viability of these markets in conducting economic research. The data consist of every transaction in a market with over one million players over three years of real time. We find that 1) the game markets are efficient, 2) the complexity of the product determines information diffusion times, and 3) we can classify which and how players participate in trade
