The conventional explanation for strikes is that they are caused by an asymmetry of information about the profitability of the firm – union members are uninformed whereas management are informed. Instead, this paper builds a model of strikes where a perception of unfairness provides an expressive benefit to vote for a strike. The asymmetry of information is now reversed such that management are uninformed about the emotionality of union members. The model predicts that larger union size increases both wage offers and the incidence of strikes. An empirical test using UK data provides support for the predictions. In particular, union size is positively correlated with the incidence of strikes and other industrial actions, even when asymmetric information regarding profitability is controlled for.