Civic Crowdfunding (CC) uses the ``power of the crowd'' to garner contributions towards public projects. As these projects are non-excludable, agents may prefer to ``free-ride,'' resulting in the project not being funded. For single project CC, researchers propose to provide refunds to incentivize agents to contribute, thereby guaranteeing the project's funding. These funding guarantees are applicable only when agents have an unlimited budget. This work focuses on a combinatorial setting, where multiple projects are available for CC and agents have a limited budget. We study certain specific conditions where funding can be guaranteed. Further, funding the optimal social welfare subset of projects is desirable when every available project cannot be funded due to budget restrictions. We prove the impossibility of achieving optimal welfare at equilibrium for any monotone refund scheme. We then study different heuristics that the agents can use to contribute to the projects in practice. Through simulations, we demonstrate the heuristics' performance as the average-case trade-off between welfare obtained and agent utility.

翻译：公民群众基金(CC)使用“人群的力量”为公共项目募集捐款。由于这些项目是不可排除的,代理商可能更喜欢“免费”项目,导致项目没有资金。对于单一项目CC,研究人员提议向激励代理商提供退款,从而保证项目的资金。这些供资担保只有在代理商拥有无限预算的情况下才适用。这项工作侧重于组合设置,为CC提供多个项目,代理商的预算有限。我们研究某些可以保证资金的具体条件。此外,如果由于预算限制无法为每个可用的项目提供资金,那么为项目的最佳社会福利子集提供资金是可取的。我们证明不可能在任何单体退款计划达到平衡的最佳福利。我们随后研究代理商能够用来为实际项目作出贡献的不同偏差。我们通过模拟,将超自然学表现作为获得的福利和代理商效用之间的平均交易。