Many private and public organizations rely on voluntary contributions to provide public goods. In order to sustain these organizations, the question arises how the willingness to contribute can be maintained and further encouraged.

In our research, we study voluntary blood donations. These voluntary contributions are necessary to keep up the highly developed medical services in many countries.

Study 1

In study 1, we examine a decision framework in which people are individually asked to either actively consent to or dissent from some prosocial behavior. We hypothesize that confronting individuals with the choice of whether to engage in a specific prosocial behavior contributes to the formation of issue-specific altruistic preferences, while simultaneously involving a commitment. The hypothesis is tested in a large-scale field experiment on blood donation. We find that this “active-decision" intervention substantially increases the actual donation behavior of people who had not fully formed preferences beforehand.

Study 2

There is a longstanding concern that material incentives might undermine prosocial motivation, leading to a decrease in blood donations rather than an increase. This paper provides an empirical test of how material incentives affect blood donations in a large-scale field experiment spanning three months and involving more than 10,000 previous donors. We examine two types of incentive: a lottery ticket and a free cholesterol test. Lottery tickets significantly increase donations, in particular among less motivated donors. The cholesterol test leads to no discernable impact on usable blood donations. If anything, it creates a small negative selection effect in terms of donations that must be discarded.