REWARD STRUCTURES IN PUBLIC GOOD EXPERIMENTS

We contrast results from a laboratory experiment in voluntary contribu tions for a public good using two reward structures with interior equi libria. The first induces a set of Nash equilibria, all sharing the sa me total donations. The second induces a unique dominant-strategy equi librium. Apparently, donor confusion over the Nash concept and coordin ation problems explain at most a small portion of the 'excessive' givi ng observed in those previous experiments that use an interior Nash de sign. Thus, we strengthen the case for interpreting experimental resul ts as consistent with altruistic preferences that are not easily overc ome by experimental induction.