Three theoretical non-point water pollution control schemes were tested repeatedly in experimental studies tax-subsidy scheme (K. Segerson, 1988), collective fining (Xepapadeas, 1991) and random fining (Xepapadeas, 1991). Camacho and Requate (2004) summarized results reported by Spraggon (2002), Vossler et al (2002), Cochard et al (2002), and Alpizar et al (2004) and replicated their experiments. In this paper I will discuss similarity and differences among all the reported results and in particular the following two. First, both collective fining and random fining induce abatement under the target, their performance deteriorates over time, and is relatively consistent over the replications. Second, tax-subsidy scheme induced abatement over the target, its performance is consistent over time, but not over the replications. Three different theories offer an explanation of how individuals behave as members of a group: non-cooperative game theory (individuals choose to maximize their individual profits), cooperative game theory (individuals within a group choose a coalition that would maximize profit of each member of the coalition), evolutionary game theory (individuals choose to maximize their relative profits difference between individual profit and average profit in the group). Each of these theories suggests a specific equilibrium for each of the nonpoint control schemes mentioned above, but individually does not explain experimental results. I will demonstrate that multi-objective optimization, where individuals are interested in maximizing a bundle (individual profit; payoff from a coalition, relative profit) is consistent with experimental data and accounts for recognized individual differences in players within a group (i.e. Kurzban & Houser, 2005).
