In or out? Crowding effects in public goods with private gifts: evidence from crowdfunding

How do cumulative contributions influence subsequent giving to public goods that offer private gifts? While prior research has examined contribution dynamics in fundraising, the role of excludability — the property of preventing noncontributors from accessing the good — remains largely unexplored. We use comprehensive data from a reward-based crowdfunding platform to show that the excludability of a project significantly shapes its contribution pattern. We introduce two novel measures of excludability: one based on a good’s inherent characteristics and another derived from the geographic distribution of backer-project distances. Our analysis reveals that more excludable goods (such as local projects and tangible products) exhibit stronger crowding-in effects, whereas less excludable ones (such as global projects and journalism) experience crowding-out effects. Although crowdfunding platforms systematically highlight cumulative contributions, our findings suggest that fundraisers should emphasize this information, particularly for excludable goods, but not for the least excludable ones.