This paper has been superseded by WP 15-03.<p>The authors document the spatial concentration of more than 1,000 research and development (R&D) labs located in the Northeast corridor of the U.S. using point pattern methods. These methods allow systematic examination of clustering at different...</p>

This working paper supersedes WP 12-22, WP 11-42, and WP 10-33. We employ a unique data set to examine the spatial clustering of private R&D labs, and, using patent citations data, we provide evidence of localized knowledge spillovers within these clusters. Jaffe, Trajtenberg, and Henderson...

Despite much theorizing about the role of geographic concentration of employment in knowledge spillovers, local densities' role in promoting innovations has largely been unexamined. More often, studies have considered the effects of city size variables on innovative activity, although the role...