This article proposes an empirical test of whether aggregate economic behavior maps from the real to the virtual. Transaction data from a large commercial virtual world — the first such data set provided to outside researchers — is used to calculate metrics for production, consumption and money supply based on real-world definitions. Movements in these metrics over time were examined for consistency with common theories of macroeconomic change. The results indicated that virtual economic behavior follows real-world patterns. Moreover, a natural experiment occurred, in that a new version of the virtual world with the same rules came online during the study. The new world's macroeconomic aggregates quickly grew to be nearly exact replicas of those of the existing worlds, suggesting that `Code is Law': macroeconomic outcomes in a virtual world may be explained largely by design structure.

Peer-to-peer sharing networks have seen explosive growth recently. In these networks, sharing files is completely voluntary, and there is no financial reward for users to contribute. However, many users continue to share despite the massive free-riding by others. Using a large-scale data set of individual activities in a peer-to-peer music-sharing network, we seek to understand users' continued-sharing behavior as a private contribution to a public good. We find that the more benefit users “get from” the network, in the form of downloads, browses, and searches, the more likely they are to continue sharing. Also, the more value users “give to” the network, in the form of downloads by other users and recognition by the network, the more likely they are to continue sharing. Moreover, our findings suggest that, overall, “getting from” is a stronger force for the continued-sharing decision than “giving to.”