It once took two decades to replace one-third of the Fortune 500; now a subset of new firms are challenging and displacing this elite group at a breathtaking rate, while armies of startups come and go within just a few years. Most new jobs are, in fact, coming from small firms, reversing the trend of a century. David Audretsch takes a close look at the U.S. economy in motion, providing a detailed and systematic investigation of the dynamic process...