The experimental literature suggests that contributions to a public good made dynamically, over multiple stages are higher than contributions made in a static setting, even when players do not receive feedback about co-players’ previous contributions between stages. Because the dynamic setting without feedback is strategically equivalent to the static one, this finding is puzzling. One important difference between the two settings, however, is that the dynamic setting gives the opportunity to sink contributions while in the static one this opportunity does not exist. I test whether the sunk character of the dynamic contributions explains the higher contributions in the dynamic setting. Symmetric players contribute in two stages to a threshold public good and receive feedback after each stage. The experimental treatment differ in whether the first-stage contributions are sunk or not when deciding on the second-stage contributions. The results show that making the first-stage contributions sunk increases the second-stage individual contributions, and this is more so the case at higher levels of the first-stage contributions. This suggests that the sunk contributions do, at least partially, explain the better performance of the dynamic setting.

实验文献表明，即使在参与者没有收到有关共同参与者先前在两个阶段之间的贡献的反馈的情况下，在多个阶段中对公共物品的动态贡献也要高于静态情况下的贡献。由于没有反馈的动态设置在策略上与静态设置等效，因此这一发现令人费解。但是，这两种设置之间的一个重要区别是，动态设置提供了降低贡献的机会，而在静态设置中则没有这种机会。我测试了动态贡献的下沉特性是否可以解释动态设置中的较高贡献。对称的参与者在两个阶段为公共物品的起征点做出贡献，并在每个阶段之后获得反馈。在确定第二阶段的贡献时，实验方法的不同之处在于第一阶段的贡献是否沉没。结果表明，使第一阶段的贡献沉没会增加第二阶段的个人贡献，而在第一阶段的贡献较高的情况下更是如此。这表明，下沉的贡献至少部分地解释了动态设置的更好性能。