The importance of knowledge spillovers in economic growth and economic development is certainly not new – its roots go back to at least the 1920s and the work of economist Alfred Marshall. Economists Friedrich Hayek and Thomas Sowell, among others, have demonstrated the crucial role that knowledge plays in private and public decision-making. More recently, academic research into the production and diffusion of knowledge has become more prevalent as the value of knowledge spillovers and knowledge networks has become apparent. To many policymakers and business leaders, the economic success of high-tech regions such as California’s Silicon Valley and Massachusetts’ Route 128 is obvious evidence of the importance of industrial clusters in fostering innovation. While tremendous gains have been made in recent decades, there still exist considerable gaps in our understanding of knowledge spillovers. For example, empirical research clearly demonstrates that a firm’s location relative to...