[en] The World Energy Council (WEC), in collaboration with global management consulting firm Oliver Wyman, have prepared the fifth edition of the World Energy Trilemma report. This second of a two-part series of reports examines the drivers and risks preventing the development of sustainable energy systems. It then recommends an Agenda for Change to address these risks and to accelerate a global transition to more diversified, and therefore sustainable, energy systems that will present opportunities for economic growth. In response to the 2012 World Energy Trilemma report, describing the policies that more than 40 energy industry CEOs and senior executives consider are necessary to advance sustainable energy systems, the 2013 report describes what public sector stakeholders believe they need from the energy industry. It is based on interviews with more than 50 energy and environmental ministers, policymakers, government officials, representatives from multilateral development banks, international non-governmental organisations, and experts from more than 25 countries. The report also reflects the results of the 2013 Energy Sustainability Index prepared by the WEC in partnership with Oliver Wyman. The Index evaluates how well countries balance the three often conflicting goals of energy sustainability - energy security, energy equity, and environmental sustainability - what the WEC defines as the 'energy trilemma'. Each of the three legs of the trilemma is vital to the economic and social development of a country. Secure energy is critical to fuelling economic growth, energy must be accessible and affordable at all levels of society, and the impact of energy production and energy use on the environment needs to be minimised to combat climate change and maintain good air and water quality. Based on an analysis of 60 data sets used to develop 23 indicators across 129 countries (including 37 non-WEC member countries), the Index provides a comparative ranking and a balance score for how well countries manage the trade-offs among the three core elements of sustainable energy systems - energy security, energy equity, and environmental sustainability. The rank measures overall performance on the Index. For the first time the balance score highlights how well a country manages the trade-offs between each of the dimensions