Correlation in the Multiplayer Electronic Mail Game

In variants of the Electronic Mail Game (Rubinstein, 1989) where two or more players communicate via multiple channels, the multiple channels can facilitate collective action via redundancy, the sending of the same message along multiple paths or else repeatedly along the same path (Chwe, 1995 and De Jaegher, 2011). This paper offers another explanation for how multiple channels may permit collective action: parties may be able to coordinate their actions when messages' arrivals at their destinations are sufficiently correlated events. Correlation serves to fill in information gaps that arise when players are uncertain of the source of message failure, effectively strengthening messages from one player. This asymmetry in message strength in turn permits cutoff equilibria, where players take action after receiving a minimum number of confirmations.