Abstract
Much of the theoretical and experimental research on charitable giving allows for three main types of donor: pure altruists, impure altruists, and pure warm-glow givers. For none of these types should donations be increasing in the amount donated by others, and the fact that some experimental subjects do behave in this way suggests a fourth type, the "competitive giver". Our experimental results provide evidence for the existence of competitive givers. The results also suggest that most (but not all) competitive giving is a result of uncertainty about the social norm: when information about the norm is revealed, the incidence of competitive giving is much lower.