On the complementarity of prosocial norms: The case of restaurant tipping during the holidays

• We examine the interaction of two prosocial norms: restaurant tipping and generosity during the holiday season.
• I identify seasonal differences in within-customer tipping behavior using two years of tipping data from a restaurant.
• I find that people tip more, not less, during the holiday season.
• The increase in tipping during the holidays is driven by those who are already the best tippers, indicating an intrinsic motive for norms like tipping.

The literature in economics overwhelmingly supports the hypothesis that people have (pure and impure) preferences for altruism. It has also been shown that prosocial acts or norms that dictate prosocial behavior can sometimes crowd out other prosocial behaviors. This paper tests whether a well-understood prosocial norm—generosity during the holiday season (i.e., around Christmas)—crowds out or complements tipping behavior, another prosocial norm. By examining seasonal differences in within-customer tipping behavior using two years of sales data from a busy restaurant, I find that during the holiday season tipping rates are higher, not lower. This effect appears to be driven by those who are already generous. The finding suggests that individuals do not necessarily view two prosocial norms as competing; rather, such norms can be complementary. Motives for prosocial norms like tipping are discussed.