# The Vote with the Wallet Game: Responsible Consumerism as a Multiplayer Prisoner's Dilemma
## 1 Introduction  
The vote with the wallet is a phenomenon of growing relevance in the contemporary economic scenario. We understand the _vote with the wallet_ as the propensity of consumers to consider social and environmental sellers' responsibility into consumption and saving choices, in order to stimulate companies to'retail' bundles of private and public goods [1] which may ultimately be in consumers' and investors' own interest (e.g., in terms of healthier food, better job opportunities, and higher corporate fiscal responsibility). Consumers may interpret their consumption as a voting behaviour [2] to send general messages to governments and other citizens, increase activism and engagement, and boost sustainable development [3]. Other consumers who are not aware of their political consumerisms, however, also face purchase decisions between responsible and non-responsible products. In this introduction we describe four examples showing how the vote with the wallet is currently working. These real-life examples document the empirical relevance of the theoretical approach we develop in our paper. The model outlined in the second section explains why the vote with the wallet is a special case of multiplayer Prisoner's Dilemma (PD): each consumer voting with the wallet for the responsible product produces a positive externality for the other consumers, because her vote contributes to the public good benefit of a higher sociallyand environmentally responsible stance of sellers. However, voting with the wallet for the responsible product may imply an extra cost vis-a-vis buying a conventional product. This extra cost may or may not be compensated by a third component, that is the intrinsic satisfaction produced by the responsible purchase for those consumers who have other-regarding preferences. These three basic ingredients of the game--the positive externality, the extra cost, and the other-regarding preferences--make free riding (i.e., buying the conventional product) the optimal strategy under a reasonably wide range of parametric conditions, thereby producing a classic coordination failure problem with a pure Nash equilibrium Pareto dominated by the strategy pair where both players vote with the wallet for the responsible product. The paper investigates various potential solutions to this coordination failure problem, in various theoretical frameworks ranging from one-shot two-player to repeated multiplayer games. A first example of responsible vote with the wallet in action is socially responsible (SR) consumption. The Global Report on Socially Conscious Consumers, one of the most extensive worldwide surveys on consumer choices [4], observes that 46 percent of interviewed consumers are willing to pay more for socially and environmentally sustainable products. The share grows to 55 percent in the 2014 Nielsen Survey. Even though contingent evaluations as those mentioned above tend to be upward biased [5], actual market shares of products being traditionally object of responsible vote with the wallet document that the phenomenon exists and is relevant. One of the most interesting examples is Fair Trade (FT). FT is a supply chain in which importers decide to transfer to marginalized raw material producers a higher share of value added than what otherwise would have been the case in order to finance their empowerment, skill upgrading, and provision of public goods to the local community (for the literature on FT see, among others, [6; 7; 8; 9], and [10].). Sales of FT products which publicly advertise their extra social and environmental component have considerably grown over the last years despite stagnating consumption in high-income countries after the global financial crisis. They were 33 percent higher in Germany, 26 percent in The Netherlands, 28 percent in Sweden, 25 percent in Switzerland, and 16 percent in the UK in 2012, compared to 2011. Empirical evidence documents that the vote with the wallet for FT products has triggered partial imitation of profit maximizing incumbents.