Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
The assurance contract mechanism is often used to crowdfund public goods. This mechanism has weak implementation properties that can lead to miscoordination and failure to produce socially valuable projects. To encourage early contributions, we extend the assurance contract mechanism with refund bonuses rewarded only to early contributors in the event of fundraising failure. The experimental results show that our proposed solution is very effective in inducing early cooperation and increasing fundraising success. Limiting refund bonuses to early contributors works as well as offering refund bonuses to all potential contributors, while also reducing the amount of bonuses paid. We find that refund bonuses can increase the rate of campaign success by 50% or more. Moreover, we find that even taking into account campaign failures, refund bonuses can be financially self-sustainable suggesting the real world value of extending assurance contracts with refund bonuses.