Continuous Preferences and Discontinuous Choices: How Altruists Respond to Incentives

This paper models two discontinuities that have been claimed to constitute important exceptions to the standard economic theory of human motivation. The first is a discontinuity in the distribution across population types of the willingness to accept payment in return for certain services such as giving blood, because such services given free are more worthwhile than when performed for payment. The second is that people who give services free may refuse to sell them for some positive price (this is known as crowding out). The paper models both phenomena when individuals act to signal their type in a two-period game with assortative matching. The former is the unique equilibrium of a signaling game in which individuals announce the prices at which they will perform a civic action. The latter may be observed as one of two equilibria of a screening game in which individuals have only a binary participation decision available to signal their type.