Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We use a new data set collected by means of a questionnaire study of volunteers of the German Red Cross to test predictions of three competing economic models of volunteer labour supply: the public-goods model, the private-consumption model and the human-capital model. The three competing economic models make different predictions regarding the response of a volunteer's labour supply to a change in the perceived labour supply of other volunteers. Our empirical results lend support to the public-goods model.