and other environmental externalities associated with the burning of fossil fuels. GPMDG was overall successful in making substantial progress towards the sustainability goals it set for its members. It is also highly valued by members. Several key factors contributed to the successful implementation of the partnership. These can be summarized as follows.

Incentives to partner: The partnership was designed by its convening organization, the WRI, so as to engage companies which had already demonstrated interest in environmental leadership and sustainable energy. This facilitated the organization of a self-enforcement initiative and minimized the reputation risk that WRI as an environmental organization might have incurred by collaborating with large corporations. Only one of the original GPMDG members had to leave the partnership due to insufficient commitment to green power development. The specific quantitative target of the partnerships was also selected by the members themselves, ensuring ownership of and commitment to the process.

Organization and Governance: GPMDG was carefully structured with a view to its functional objectives. The adoption of a measurable sustainability target safeguarded its environmental integrity. Membership is kept small to facilitate more productive learning and open sharing of information. To this end, partners sign an information non-disclosure agreement and new members are only admitted with unanimous approval. Only companies which are not direct competitors can participate. WRI staff maintains one-to-one contact with member companies, tailoring technology research to their specific needs. Through quarterly annual meetings (held 3 times a year since 2008), partners showcase some of the technologies implemented and share experience and knowledge on advantages and hurdles of technology options and their implementation. Since close to 80-90 percent of the membership attends each meeting, there is no formal governance body such as an Executive Board or Executive Committee. Decision with respect to pursuing (or not) a specific green power project are managed internally by the member companies.

Implementation and Outcomes: In the case of GPMDG, contrary to many partnerships, it is relatively unproblematic to assess implementation. As of March 2008, the 15 GPMDG-US companies have purchased or implemented 733.5 MW toward the 1000 MW objective, indicating that there is a high likelihood that the group would achieve its target of 1,000MW of green power by 2010. Another tangible outcome of the partnership is the demonstration of a wide array of green energy technologies. Of the 733.5MW of green energy developed, 471.8 MW was purchased in the form of wind Renewable Energy Certificates (RECs), 31 MW from biomass RECs, and 24.4MW from landfill gas RECs. In addition, the group has facilitated the development of 34.8 MW of wind power, 72.8 MW landfill gas and biomass based energy, 44.5MW of low impact hydro,