This paper uses a gravity framework to investigate the effects of distance as well as subnational and national borders in knowledge spillovers. Drawing on the NBER Patent Citations Database, we examine patent citations data at metropolitan level within the U.S. and the 38 largest patent-cited...

This paper analyzes China’s trade relationships using a new trade intensity index, which incorporates gravity model estimation, to compare observed trade levels with levels would be expected to prevail given the economic, geographic, and cultural characteristics of the trading partners. The...