This report documents the development of the baseline projection to 2050 for use in the CGE modelling work contained in WP7. The main purpose of the baseline construction is to establish a likely business-as-usual scenario towards 2050, against which the transboundary effects of alternative EU decarbonization pathways can be estimated. The main components of the baseline are annual GDP projections and associated drivers such as population, labor force, capital stock, and total factor productivities for individual countries including all EU Member States. The principal data sources are recent model-based projections, particularly the EU-Reference Scenario 2016 and various other projections related to the SSP2 scenarios. Additionally, this report contains a review of the existing modelling approaches towards baseline constructions and a discussion on how the baseline can be replicated/calibrated within the EUCalc framework. A brief review on the CGE model selection and on how to represent the alternative EU decarbonization pathways relative to the baseline in the chosen model is also offered.