What sustains social norms and how they evolve? The case of tipping

The paper presents a model of the evolution of social norms. When a norm is costly to follow and people do not derive benefits from following it except for avoiding social disapproval, the norm erodes over time. Tip percentages, however, increased over the years, suggesting that people derive benefits from tipping, such as impressing others and improving their self-image as being generous and kind. The implications to the norm of not cooperating with new workers who accept lower wages are discussed; the model suggests that incumbent workers have reasons to follow this norm in addition to avoiding social disapproval.