Early contributors and fair rewards in crowdfunding

We address the issue of fairly rewarding contributors to a crowdfunded project. We develop a theoretical non-strategic model, and introduce a new reward rule: a contributor’s reward depends both on her financial contribution and on the timing of her contribution. Following the axiomatic method used in models of resource sharing, we characterize this new reward rule by a pair of natural axioms. The resulting rewards coincide with the Shapley value of a suitable cooperative game built from the crowdfunding project. This allocation rule conveys a signaling effect: if two contributors make the same financial contribution, the earlier obtains a greater reward.