Using data on academic citations, career histories of mathematicians, and disaggregated distance data for the world's top 1000 math departments, we study how geography and personal ties affect knowledge flows among scholars. The ties we consider are co-authorship, past co-location, advisor-advisee relationships, and alma mater relationships (holding a Ph.D.~from the institution where another scholar is affiliated). Using matched choice-based sampling logit regressions, we find that linkages significantly facilitate knowledge flows. Controlling for ties generally halves the negative impact of geographic barriers on citations. Ties matter more for less prominent and more recent papers. Proximity continues to influence knowledge flows even in the era of Google searches.
- knowledge spillovers,
- paper citations,
Available at: http://works.bepress.com/yaoamberli/6/