Using a large natural field experiment, we demonstrate that a small unconditional gift (pen) more than doubled both small (survey) and large (blood donation) responses. We find no evidence that the opportunity for a small response crowded out the larger response; asking participants to also...

This paper examines substitution effects across charitable donations, specifically the effect of 2nd collections on 1st collections at Catholic Masses. While 2nd collections increased total donations by 17.8%, 18.4% of 2nd collection donations came from 1st collections which fell 4.3%.