Do community needs affect the decision to volunteer? The case of refugees in Germany

I study the relationship between changes in community needs and the supply of voluntary work. I present basic theoretical considerations, which suggest that the relationship between voluntary work and an increase in community needs is ambiguous. Then, I test the relationship empirically by proxying community needs with the number of needy people, i.e., refugees, in a county, and by exploiting the quasi-random allocation of refugees within Germany. I find that doubling the number of refugees increases the probability of volunteering by about 2 percentage points. These estimates imply that 1.45 million people additionally volunteered during the refugee crisis, i.e., more than one person per refugee.