This book addresses the rising productivity gap between the global frontier and other firms, and identifies a number of structural impediments constraining business start-ups, knowledge diffusion and resource allocation (such as barriers to up-scaling and relatively high rates of skill mismatch).Analysis based on micro and industry-level data highlights the importance of reallocation-friendly policies, including well-functioning product, labour and risk capital markets, efficient judicial systems, bankruptcy laws that do not excessively penalise failure, housing policies that do not unduly restrict labour mobility, and improvements in public funding and organisation of basic research which do not excessively favour applied vs basic research and incumbents vs young firms.