Surveys of socially desirable behavior are susceptible to [socially desirable responding](https://en.wikipedia.org/wiki/Social-desirability_bias https://en.wiki

Surveys of socially desirable behavior are susceptible to [socially desirable responding](https://en.wikipedia.org/wiki/Social-desirability_bias https://en.wikipedia.org/wiki/Social-desirability_bias). It's unclear how, or if, this particular survey accounted for such bias. On the broader topic of tipping, I think of it as a tax on nice people.