How Cheap Talk Enhances Efficiency in Public Goods Games

This paper uses a Bayesian mechanism design approach to investigate the effects of  communication in a threshold public goods game.  Individuals have private information about contribution costs.  If at least some fraction of the group makes a discrete contribution, a public benefit accrues to all members of the group.  We experimentally implement three different communication structures prior to the decision move:  (a) simultaneous exchange of binary messages, (b) larger finite numerical message space, and (c) unrestricted text chat.  We obtain theoretical bounds on the efficiency gains that are obtainable under these different communication structures.  In an experiment with three person groups and a threshold of two, we observe significant efficiency gains only with the richest of these communication structures, where participants engage in unrestricted text chatting.  In that case, the efficiency bounds implied by mechanism design theory are achieved.