Sunspots in global games : theory and experiment

We solve and test experimentally a global-games model of speculative attacks where agents can choose whether to read, at a cost, a payoff irrelevant (sunspot) announcement. Assuming that subjects exogenously believe some others to follow sunspots, we provide conditions for a unique equilibrium where agents follow a sunspot announcement depending on the realization of an informative private signal. Although most groups converge to classical global-game strategies that neglect sunspots, we find that about one-third of groups are eventually coordinating on sunspots, which is inconsistent with the standard theory. In line with the assumption of subjects expecting others to follow sunspots, subjects overestimate the number of subjects who follow sunspots by about 100% on average. We conclude that in environments with high strategic uncertainty, payoff irrelevant signals can affect behavior even if they are costly to obtain and not expected to be publicly observed.