  I study a social learning model in which the object to learn is a strategic
player's endogenous actions rather than an exogenous state. A patient seller
faces a sequence of buyers and decides whether to build a reputation for
supplying high quality products. Each buyer does not have access to the
seller's complete records, but can observe all previous buyers' actions, and
some informative private signal about the seller's actions. I examine how the
buyers' private signals affect the speed of social learning and the seller's
incentives to establish reputations. When each buyer privately observes a
bounded subset of the seller's past actions, the speed of learning is strictly
positive but can vanish to zero as the seller becomes patient. As a result,
reputation building can lead to low payoff for the patient seller and low
social welfare. When each buyer observes an unboundedly informative private
signal about the seller's current-period action, the speed of learning is
uniformly bounded from below and a patient seller can secure high returns from
building reputations. My results shed light on the effectiveness of various
policies in accelerating social learning and encouraging sellers to establish
good reputations.
