One bad apple spoils the barrel? Public good provision under threshold uncertainty

We report laboratory evidence on the voluntary provision of threshold public goods when the exact location of the threshold is not known. Our experimental treatments explicitly compare two prominent technologies, summation, and weakest link. Uncertainty in threshold location is particularly detrimental to threshold attainment under weakest link, where low contributions by one subject cannot be compensated by others. In contrast, threshold uncertainty does not affect contributions under summation. We demonstrate that non-binding pledges improve the chances of threshold attainment under both technologies, particularly under weakest link.