The Relative Eectiveness of Incentives: Previous evidence from survey studies suggests
that blood donors prefer being oered a health test rather than a material reward such as a
lottery ticket (Glynn et al., 2003). This is in stark contrast to the prediction from any model
in economics, that, holding the monetary value constant, individuals will prefer cash rewards
over in-kind rewards. In our case, the retail price of the cholesterol test is about three times the
price of the lottery ticket. Thus, a prediction of the relative eectiveness based on the economic
model is not possible. We therefore contrast our behavioral evidence with the survey evidence
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on blood donors' attitudes towards various kinds of rewards.