The social contagion of prosocial behaviour: How neighbourhood blood donations influence individual donation behaviour.

Life-saving transfusions and numerous other medical treatments are enabled by a minority of people that donate blood. But why do some people repeatedly engage in such prosocial behaviour, especially when it is costly to themselves? This study examines to what extent social contagion within neighbourhoods - changing behaviour in response to the behaviour of others - affects repeated blood donation behaviour. We draw on longitudinal survey and register data from a representative sample of blood donors in the Netherlands from 2007 to 2014 (N = 15,090). Using a panel data model and an instrumental variable approach, we find that donors are positively affected by donations made by other donors living in their neighbourhood. This effect does not seem to be mediated by normative or informational social influence. Exploratory analysis further attributes this finding to social contagion within donor couples. Our study contributes to the literature on repeated blood donation behaviour, and can inform retention strategies of blood banks.