This project brings together experienced researchers and rising young stars to investigate the emerging new trends in the inequality across firms. The goals are to establish the facts of increasing firm differences in the U.S. while providing some context through a summary of international comparative evidence; to understand the causes of these changes; to explore the macro-economic implications of the trends; and to provide a foundation for public policy discussions. The project will focus primarily on empirical work. The research carried out in connection with this project will inform a range of key policy questions, including whether firm differences have contributed to increased market power and also rising income inequality, and whether there are policy levers -- anti-trust, other regulatory initiatives, trade policies, or others – that could affect these developments.