Before revision:  We provide a simple linear formula characterizing agents' actions in terms of network paths and use this formula to determine when society eventually learns correctly . Disproportionately influential early agents can cause herding on incorrect beliefs and we compute comparative statics of the probability of  herding with respect to network parameters.
After revision:  We provide a simple linear formula characterizing agents' actions in terms of network paths and use this formula to completely characterize the set of networks allowing eventual correct learning . Disproportionately influential early agents can cause herding on incorrect beliefs and we compute comparative statics of the probability of herding with respect to network parameters.