Heterogeneous productivity stabilizes public good contributions under certainty, uncertainty and ambiguity

Typically, a linear public goods game with a voluntary contribution mechanism (VCM) sees declining contributions over repeated one-shot periods of play. However, contributions under uncertainty or ambiguity over heterogeneous productivity on individual contributions have yet to be investigated. We compare contributions under homogenous productivity of 0.6; and certain, uncertain (for future periods only and all periods) or ambiguous heterogeneity in productivity, which can be either a high (0.9) or a low (0.3) type. Certain heterogeneity unexpectedly stabilizes contributions over homogenous, led by high productivity types. Uncertain or ambiguous heterogeneity in productivity weakly lowers contributions, but they remain stable. Thus, in a novel finding that is replicated across our treatments, heterogeneous productivity appears to support stable contributions over time, even when productivity is unknown at time of contribution. This finding suggests uncertain and heterogeneous productivity are an important characteristic of public goods that needs to be considered when modelling them in the field, and reinforces the role of productivity itself in driving voluntary public good contributions.