Fair Rewards in Crowdfunding: Balancing Contribution and Timing

The authors look at how to fairly reward people who contribute to a crowdfunded project. They create a model that isn’t based on strategy and introduce a new rule for rewards: a person’s reward depends on both how much money they give and when they give it. Using a method often used in sharing resources, they define this reward rule based on two simple fairness principles. The final rewards match a well-known idea from game theory called the Shapley value, which helps divide rewards fairly. Their rule also sends a clear message: if two people give the same amount, the one who donates earlier gets a bigger reward.


Early contributors and fair rewards in crowdfunding

Béal, S., Deschamps, M., Refait-Alexandre, C. et al. Early contributors and fair rewards in crowdfunding. Theory Decis 98, 33–59 (2025). https://doi.org/10.1007/s11238-024-09996-6 

Can Every City Be a 15-Minute City?

The idea of a "15-minute city" has gained a lot of attention recently. This concept envisions cities where you can reach essential services, like schools, stores, and parks, within a 15-minute walk or bike ride. While this idea is exciting and has started important conversations about how cities should be designed, it isn’t practical everywhere, and there are challenges with how it’s defined.

This research explores how close cities around the world are to meeting the 15-minute city ideal. By measuring how quickly you can access important services, it becomes clear that access varies widely both within and between cities. A big factor is how densely populated areas are.

An online tool (https://whatif.sonycsl.it/15mincity/) allows you to explore access scores for almost any city in the world. The research also examines how better planning and resource distribution could reduce inequalities in access. The results show significant differences in the number of extra services cities would need to meet the 15-minute city standard.

To make this concept work for more cities, it should be adapted to fit local conditions, including population density and cultural needs. Instead of focusing only on time, cities should also prioritize what you and others value most.

Bruno, M., Monteiro Melo, H.P., Campanelli, B. et al. A universal framework for inclusive 15-minute cities. Nat Cities 1, 633–641 (2024). https://doi.org/10.1038/s44284-024-00119-4