Balanced Donor Coordination: Efficient Fair Distribution of Charity

Charity is typically done either by individual donors, who donate money to charities they support, or by centralized organizations such as governments or municipalities, which collect individual contributions and distribute them among a set of charities. Individual charity respects the will of the donors, but may be inefficient due to a lack of coordination; centralized charity is potentially more efficient, but may ignore the will of individual donors.

 We present a mechanism that combines the advantages of both methods. It distributes the contribution of each donor in an efficient way, such that no subset of donors has an incentive to redistribute their donations.
Assuming Leontief utilities (i.e., each donor is interested in maximizing an individually weighted minimum of all contributions across the charities), our mechanism is group-strategyproof, preference-monotonic, contribution-monotonic, maximizes Nash welfare, and can be computed using convex programming.
For Leontief utility functions with binary weights, the mechanism we propose is egalitarian both for projects and donors, and can be computed via linear programming and a best-response dynamics.

A full version of this paper can be found at https://arxiv.org/abs/2305.10286 .