Abstract
The problem of public good provision is central in economics and touches upon many challenging societal issues, ranging from climate change mitigation to vaccination schemes. However, results which are supposed to be applied to a societal scale have only been obtained with small groups of people, with a maximum group size of 100 being reported in the literature. This work takes this research to a new level by carrying out and analysing experiments on public good games with up to 1000 simultaneous players. The experiments are carried out via an online protocol involving daily decisions for extended periods. Our results show that within those limits, participants’ behaviour and collective outcomes in very large groups are qualitatively like those in smaller ones. On the other hand, large groups imply the difficulty of conveying information on others’ choices to the participants. We thus consider different information conditions and show that they have a drastic effect on subjects’ contributions. We also classify the individual decisions and find that they can be described by a moderate number of types. Our findings allow to extend the conclusions of smaller experiments to larger settings and are therefore a relevant step forward towards the understanding of human behaviour and the organisation of our society.
Highlights
Departamento de Análisis Económico, Facultad de Economía, Universidad de Valencia, Avenida de los Naranjos s/n, The most studied paradigm for this problem is the public good game[1] (PGG), where participants receive an endowment and decide how much of that endowment they want to contribute to a common pool
The first results were obtained by Isaac et al.[19], finding a positive group size effect, average cooperation increased, for a marginal per-capita return (MPCR) of 0.3 but not for an MPCR of 0.75
The Marginal Per Capita Return (MPCR) was 0.1 for all experiments, except for the PGG1000 were it was 0.01 to ensure comparison with the control treatment, preserving the ratio “multiplication factor/endowment”–that is, the pool return with respect to the endowment
Summary
Departamento de Análisis Económico, Facultad de Economía, Universidad de Valencia, Avenida de los Naranjos s/n, The most studied paradigm for this problem is the public good game[1] (PGG), where participants receive an endowment and decide how much of that endowment they want to contribute to a common pool. Following Diederich et al.[13], we will consider large groups those consisting of 20 or more people and, as we will discuss below, only a handful of experimental results obtained using PGG are available. The first results were obtained by Isaac et al.[19], finding a positive group size effect, average cooperation increased, for a marginal per-capita return (MPCR) of 0.3 but not for an MPCR of 0.75. In a more recent work, Weimann et al.[20] run PGG experiments with 30 and 40 participants and MPCRs between 0.04 and 0.12, and groups with 100 participants and MPCRs between 0.02 and 0.04 Their results show that, as far as first round contributions are concerned, small and large groups behave . We have found that the dropout rate during a two-week-long experiment is less than 20%, certainly a non-negligible value that either calls for measures to mitigate it or asks for further analysis to quantify how it affects the conclusions of these experiments
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