In public good games, voluntary contributions tend to start of high and decline as the game is repeated. If high contributors are matched, however, contributions tend to stay high. We propose a formalization predicting that high contributors will selfselect into groups committed to charitable...

Work contributes to people's self-image in important ways. We propose a model in which individuals have a preference for being important to others. This leads to the following predictions: 1) In fully competitive markets with performance pay, behavior coincides with the standard model (bakers)....