Using patent citation data for the U.S., we test whether knowledge spillovers in biotechnology are sensitive to distance, and whether that sensitivity has changed over time. Controlling for self-citation by inventor, assignee and examiner, cohort-based regression analysis shows that physical...

This paper sheds light on the questions, Why does knowledge spill over? and How does knowledge spill over? The answer to these questions we suggest lies in the incentives confronting scientists to appropriate the expected value of their knowledge considered in the context of their path-dependent...