The FEEM Sustainability Index (FEEM SI) is the first aggregate index able to provide future projections of sustainability of countries, allowing for comparisons not only across countries, but also through time. Built from a selection of over-arching indicators chosen among the most well-known and reliable international datasets, the FEEM SI manages to condense in a unique way the information included in each of its components, using a novel aggregation methodology that exploits all the interactions across indicators.