Before revision:  which lets us compare the aggregative efficiency of social learning across networks . Learning is very inefficientin a class of networks where agents move in generations and observe the previous generation  . Generations after the first contribute very little additional information  , even when generations are arbitrarily large.
After revision:  which lets us compare the aggregative efficiency of social learning across networks . Learning is very inefficientin a class of networks where agents move in generations and observe the previous generation , aggregative efficiency is a simple function of network parameters: increasing in observations and decreasing in confounding . Generations after the first contribute very little additional information , even when generations are arbitrarily large.