We extend the model of Delfgaauw and Dur (2010) to analyze the occupation choice with the presence of the public service motivation. When the workers are purely altruistic, the lower is the acceptance rate of job application to the public sector, the higher is the possibility to have applicants with better managerial ability. In addition, when the friction cost of restarting job searching is higher, the applicants with less managerial ability tend to apply the private sector jobs from the beginning. On the other hand, when the workers are impurely altruistic, the applicants with less managerial ability will not self-select into the public sector. Finally, the highest social welfare level may not be reached if the acceptance rate in the public sector is not one hundred percent.

The aim of this thesis is to present and analyse the role of the environmental groups and the trade unions on the issue of the environmental protection through the economic methodology. The specific groups have strong connection with the environmental issue since the beginning of the environmental movement. However, the two groups stand on different positions in the market and in the society, therefore they have different objectives and different tools for the achievement of their targets. Following the groups' different characteristics, I analyse their targets and how these could influence the firms' technological choice, the level of the production, the profits and finally the level of the emissions released by the firms' production. In the second chapter, a deeper analysis on the behavior and the strategy of the environmental groups is provided in order to shed more light on their objectives from the beginning of the environmental movement. Following a review of the literature an analytical framework for studying targets or motivations of the environmental groups is analysed. Three interrelated factors which affect the strategy and the decisions of the group are identified; the group s size, their budget and the weight of impure altruism in their individual and collective objectives. A positive relation exists between the group s size and the financial contributions, and the interaction of the personal expectations with the collective objectives encourages and benefits the group s actions. In the third chapter following the experience from the real world, the participation of the environmental groups in the emissions trading system (ETS) is analysed. Concretely, a competition in an ETS as a game between two firms and environmental group is modelled. According to the results, there is a U-shape relationship between how polluting the chosen technology is and the degree of the environmentalists impure altruism. Firms choose a more polluting technology in the presence of the environmentalists than in their absence if they are characterised by a high enough degree of impure altruism. Finally, in the fourth chapter the influence of the trade unions on the firms' environmental technological choice is analysed. However, in addition to the literature and according to the real world experience the unions care for the environmental protection. Particularly, the decentralised structure is compared with the centralised structure under a Cournot duopoly. I conclude that the decentralised structure could always provide higher incentives to the firms for the adoption of a better (less polluting) technology. Furthermore, there is an inverse U-shape relation between the firm s emissions and the size of the market. Finally, the emissions could be less under the centralised case compared to the decentralised for relatively low market size.