Self-love, growth, and competition in a public good game

Competition and cooperation are not always at odds and contributions to public goods are almost never one-off one-shot temporally isolated events. We examine voluntary contribution in a new public good experiment where “self-love” competitive motivations and time dynamic interdependencies are simultaneously considered. The competitive motivations are manipulated via subjects competing in each group (intragroup competition) for higher return factors on their public expenditure, whereas time dynamic interdependencies are modeled by letting returns from previous periods available for future contributions to public goods (CG). We ran two control conditions where intragroup competition (C) and time dynamic interdependencies (G) are separately implemented. Our findings showed that shares of endowment contributed were significantly greater and increasing over time when endowments growth and heterogeneous returns factors were simultaneously introduced. This effect can be attributed to return factors obtained in previous periods. Accordingly, wealth exponential growth has been greatly accelerated relative to our control condition. Distributive equity concerns have been also documented. Although Gini coefficients were significantly lower in the presence of heterogeneous return factors and endowments growth, inequality trends seemed to converge at control condition values in the long term.