Tipping is somewhat of a bizarre practice because it suggests that you are rewarding a person for a job well done. However, often times it merely reflects societal norms. For example, when I go to a restaurant, I always tip the waiter/waitress. How much I leave largely depends on the service, but their performance has to be awfully bad for me to neglect to leave a tip altogether.
I am particularly interested in situations where it is not the norm to leave a tip. For example, I went through an automated car wash this morning. After the car passes through, two or three employees of the car wash then proceed to dry the car. I may be mistaken, but this is not a situation that requires a tip by some societal norm. Some employees are better than others and, in my view, they should be rewarded with a tip. However, I do not like to roll down my window after a car wash and thus I sometimes give the tip prior to the wash.
So here are my questions. Is this efficient? Should I tip before they have completed the job? Will this provide an incentive to do a good job? My rather unscientific observations suggest that they do a good job when tipped prior to the wash. However, since I do not know any of the workers I cannot be sure that this is as a result of the tip or the natural work ethic of the employees.