  Massively multiplayer online role-playing games often contain sophisticated
in-game economies. Many important real-world economic phenomena, such as
inflation, economic growth, and business cycles, are also present in these
virtual economies. One major difference between real-world and virtual
economies is the ease and frequency by which a policymaker, in this case, a
game developer, can introduce economic shocks. These economic shocks, typically
implemented with game updates or signaled through community channels, provide
fertile ground to study the effects of economic interventions on markets. In
this work, we study the effect of in-game economic market interventions,
namely, a transaction tax and an item sink, in Old School RuneScape. Using
causal inference methods, we find that the tax did not meaningfully affect the
trading volume of items at the tax boundaries and that the item sink
contributed to the inflation of luxury good prices, without reducing trade
volume. Furthermore, we find evidence that the illicit gold trading market was
relatively unaffected by the implemented market interventions. Our findings
yield useful insights not only into the effect of market interventions in
virtual economies but also for real-world markets.
