Untold Billions: Fossil-fuel subsidies, their impacts and the path to reform is a series of papers examining the extent of fossil-fuel subsidies, their impact on climate change and sustainable development more broadly, and the challenges to their reform. The aim of this project is to take the first and necessary steps toward a better understanding of the scope and role of fossil-fuel subsidies in the world economy. The reports provide a detailed overview, setting out what is currently known about subsidies to this sector and addressing key areas that need to be tackled in order for countries to undertake reform initiatives.