If a previously unpaid activity (donating blood) is paid then we often observe that this activity is reduced. In this paper, it is hypothesised that the price offered is taken as a proxy for the "market value" of the activity. Depending on how the actor valued the activity previously,...

Models to the issue of altruism which rely on externalities of well-being are rarely used explicitly. In this paper we compare such utility-based approaches with the standard approach on altruism which is based on externalities of income. Testable differences of both types of models are derived...