The paper notes that nearly one-third of humanity still lacks access to modern energy, which is considered a critical factor in realizing sustainable development. It suggests establishing an international target for universal access to modern energy, and investigates the practicalities of measuring and reporting on such a target. The authors focus on precedents in the areas of energy and development where measurement tools have proven to be helpful indicators of development progress and have benefited policy makers. They address a number of challenges regarding measuring deficits in energy access but note that, while