Improvements in workforce skills are essential for European countries to attain higher economic growth and to compete effectively on product markets. Literature indicates a positive relationship between levels of education and productivity growth. This report builds on and expands this body of research in two ways: (1) It investigates the differential impact of various skill types--higher (academic), upper-intermediate vocational, lower-intermediate vocational, lower-intermediate general, and low--on labour productivity; and (2) It accounts for the stock of uncertified skills (i.e. those built through training). The analysis is carried out in six European Union Member States--Denmark, Germany, France, the Netherlands, Sweden, and the United Kingdom--representing different modes of vocational education and training (VET) and those for which data were available. The analysis suggests that general and vocational skills complement each other and that the effect of certified skills on productivity is stronger when certified skills are reinforced by training. This study underlines that learning in the workplace, both in initial and continuing VET, makes a fundamental contribution to productivity, and comes to support policy efforts to develop apprenticeship and adult learning. The following annex is included: (1) Overview of research methods used in the study. [This publication is the result of a team effort reflecting the work of a research consortium of Geoff Mason, Dawn Holland, Iana Liadze, Rebecca Riley, Ana Rincon-Aznar, and Mary O'Mahony, and their aids Tatiana Fic, Rachel Whitworth, Yasheng Maimaiti, and Fei Peng. This work was carried out under contract number 2009-0216/AO/RPA/GUTCHPDE/VET-Macroeconomic-benefits/010/0.]