UPDATED 2017. The main purpose of this manual is to provide inexperienced users of GEM data, the academic community and other stakeholders in the field of economics and development with relevant details on how GEM has emerged, how GEM data is collected and how the main GEM indicators should be interpreted. The manual provides comprehensive information about the theoretical model that drives the data collection, data quality control, a description of the main indicators and their correct interpretations, as well as an assessment on the validity of GEM measures.