Before revision:   We identify groupthink as the cause of this failure of information aggregation : As the number of agents grows, the actions of each individual depend more and more on the past actions of others, thus revealing less private information .
After revision:  We identify rational groupthink---in which agents ignore their private signals and choose the same action for long periods of time---as the cause of this failure of information aggregation : As the number of agents grows, the actions of each individual depend more and more on the past actions of others, thus revealing less private information .